refactor(mq_editor): consolidate duplicates, extract utils.js and app.js

- utils.js (new): evalBezier (robust), getCanvasCoords, buildBandPoints
- app.js (new): extract ~450-line inline script from index.html
- editor.js: generalize _makeJogSlider(inp, options) with onUpdate cb,
  eliminate 50-line inline resonator jog duplication, use getCanvasCoords
- mq_extract.js: extract findBestPeak(), replace two identical loop bodies
- viewer.js: remove duplicate evalBezier, use getCanvasCoords/buildBandPoints
- mq_synth.js: remove duplicate evalBezier
- index.html: inline script removed, load order: utils→fft→extract→synth→viewer→editor→app

handoff(Claude): mq_editor refactor complete — no logic changes, browser-ready.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

8 files changed, 547 insertions, 570 deletions

diff --git a/doc/COMPLETED.md b/doc/COMPLETED.md
index 3e02c40..1fb51f5 100644
--- a/doc/COMPLETED.md
+++ b/doc/COMPLETED.md
@@ -557,6 +557,15 @@ Use `read @doc/archive/FILENAME.md` to access archived documents.
 - **Task #39: Visual Debugging System**: Implemented a comprehensive set of wireframe primitives (Sphere, Cone, Cross, Line, Trajectory) in `VisualDebug`. Updated `test_3d_render` to demonstrate usage.
 - **Task #68: Mesh Wireframe Rendering**: Added `add_mesh_wireframe` to `VisualDebug` to visualize triangle edges for mesh objects. Integrated into `Renderer3D` debug path and `test_mesh` tool.
 
+#### mq_editor Refactoring (February 18, 2026)
+- **`utils.js`** (new): consolidated `evalBezier` (robust dt≤0 guard), `getCanvasCoords`, `buildBandPoints` — loaded first.
+- **`app.js`** (new): extracted ~450-line inline `<script>` from `index.html`.
+- **`editor.js`**: generalized `_makeJogSlider(inp, options)` with `onUpdate` callback; eliminated 50-line resonator jog duplication; uses `getCanvasCoords`.
+- **`mq_extract.js`**: extracted `findBestPeak`, replacing two identical loop bodies.
+- **`viewer.js`**: removed duplicate `evalBezier`; uses `getCanvasCoords` and `buildBandPoints`.
+- **`mq_synth.js`**: removed duplicate `evalBezier`.
+- **`index.html`**: inline script removed; load order: `utils.js` → fft → mq_extract → mq_synth → viewer → editor → `app.js`.
+
 #### CNN v2 Training Pipeline Improvements (February 14, 2026) 🎯
 - **Critical Training Fixes**: Resolved checkpoint saving and argument handling bugs in CNN v2 training pipeline. **Bug 1 (Missing Checkpoints)**: Training completed successfully but no checkpoint saved when `epochs < checkpoint_every` interval. Solution: Always save final checkpoint after training completes, regardless of interval settings. **Bug 2 (Stale Checkpoints)**: Old checkpoint files from previous runs with different parameters weren't overwritten due to `if not exists` check. Solution: Remove existence check, always overwrite final checkpoint. **Bug 3 (Ignored num_layers)**: When providing comma-separated kernel sizes (e.g., `--kernel-sizes 3,1,3`), the `--num-layers` parameter was used only for validation but not derived from list length. Solution: Derive `num_layers` from kernel_sizes list length when multiple values provided. **Bug 4 (Argument Passing)**: Shell script passed unquoted variables to Python, potentially causing parsing issues with special characters. Solution: Quote all shell variables when passing to Python scripts.
 
diff --git a/tools/mq_editor/app.js b/tools/mq_editor/app.js
new file mode 100644
index 0000000..059d700
--- /dev/null
+++ b/tools/mq_editor/app.js
@@ -0,0 +1,447 @@
+// MQ Editor — application glue (extracted from index.html)
+
+// LP: y[n] = k*x[n] + (1-k)*y[n-1]  => -3dB at cos(w) = (2-2k-k²)/(2(1-k))
+function k1ToHz(k, sr) {
+  if (k >= 1.0) return sr / 2;
+  const cosW = (2 - 2*k - k*k) / (2*(1 - k));
+  return Math.acos(Math.max(-1, Math.min(1, cosW))) * sr / (2 * Math.PI);
+}
+// HP: y[n] = k*(y[n-1]+x[n]-x[n-1])  => -3dB from peak at cos(w) = 2k/(1+k²)
+function k2ToHz(k, sr) {
+  if (k >= 1.0) return 0;
+  const cosW = 2*k / (1 + k*k);
+  return Math.acos(Math.max(-1, Math.min(1, cosW))) * sr / (2 * Math.PI);
+}
+function fmtHz(f) {
+  return f >= 1000 ? (f/1000).toFixed(1) + 'k' : Math.round(f) + 'Hz';
+}
+function getSR() { return (typeof audioBuffer !== 'undefined' && audioBuffer) ? audioBuffer.sampleRate : 44100; }
+
+// LP/HP slider live display
+document.getElementById('lpK1').addEventListener('input', function() {
+  const k = parseFloat(this.value);
+  const f = k1ToHz(k, getSR());
+  document.getElementById('lpK1Val').textContent = k >= 1.0 ? 'bypass' : fmtHz(f);
+});
+document.getElementById('hpK2').addEventListener('input', function() {
+  const k = parseFloat(this.value);
+  const f = k2ToHz(k, getSR());
+  document.getElementById('hpK2Val').textContent = k >= 1.0 ? 'bypass' : fmtHz(f);
+});
+
+// Show/hide global resonator params when forceResonator toggled
+document.getElementById('forceResonator').addEventListener('change', function() {
+  document.getElementById('globalResParams').style.display = this.checked ? '' : 'none';
+});
+document.getElementById('globalR').addEventListener('input', function() {
+  document.getElementById('globalRVal').textContent = parseFloat(this.value).toFixed(4);
+});
+document.getElementById('globalGain').addEventListener('input', function() {
+  document.getElementById('globalGainVal').textContent = parseFloat(this.value).toFixed(2);
+});
+let audioBuffer = null;
+let viewer = null;
+let audioContext = null;
+let currentSource = null;
+let extractedPartials = null;
+let stftCache = null;
+
+const wavFile = document.getElementById('wavFile');
+const chooseFileBtn = document.getElementById('chooseFileBtn');
+const extractBtn = document.getElementById('extractBtn');
+const autoSpreadAllBtn = document.getElementById('autoSpreadAllBtn');
+const playBtn = document.getElementById('playBtn');
+const stopBtn = document.getElementById('stopBtn');
+const canvas = document.getElementById('canvas');
+const status = document.getElementById('status');
+const fileLabel = document.getElementById('fileLabel');
+
+const hopSize = document.getElementById('hopSize');
+const threshold = document.getElementById('threshold');
+const prominence = document.getElementById('prominence');
+const freqWeightCb = document.getElementById('freqWeight');
+const birthPersistenceEl = document.getElementById('birthPersistence');
+const deathAgeEl = document.getElementById('deathAge');
+const phaseErrorWeightEl = document.getElementById('phaseErrorWeight');
+const minLengthEl = document.getElementById('minLength');
+const keepPct = document.getElementById('keepPct');
+const keepPctLabel = document.getElementById('keepPctLabel');
+const fftSize = 1024; // Fixed
+
+function getKeepCount() {
+  return Math.max(1, Math.ceil(extractedPartials.length * parseInt(keepPct.value) / 100));
+}
+
+keepPct.addEventListener('input', () => {
+  keepPctLabel.textContent = keepPct.value + '%';
+  if (viewer && extractedPartials) viewer.setKeepCount(getKeepCount());
+});
+
+// --- Editor ---
+const editor = new PartialEditor();
+editor.onPartialDeleted = () => {
+  if (viewer && extractedPartials)
+    viewer.setKeepCount(extractedPartials.length > 0 ? getKeepCount() : 0);
+};
+
+// Initialize audio context
+function initAudioContext() {
+  if (!audioContext) {
+    audioContext = new (window.AudioContext || window.webkitAudioContext)();
+  }
+}
+
+// Shared: initialize editor from an AudioBuffer
+function loadAudioBuffer(buffer, label) {
+  audioBuffer = buffer;
+  initAudioContext();
+  extractBtn.disabled = false;
+  playBtn.disabled = false;
+  setStatus('Computing STFT cache...', 'info');
+
+  // Reset partials from previous file
+  extractedPartials = null;
+  editor.setPartials(null);
+
+  setTimeout(() => {
+    const signal = audioBuffer.getChannelData(0);
+    stftCache = new STFTCache(signal, audioBuffer.sampleRate, fftSize, Math.max(64, parseInt(hopSize.value) || 64));
+    setStatus(`${label} — ${audioBuffer.duration.toFixed(2)}s, ${audioBuffer.sampleRate}Hz, ${audioBuffer.numberOfChannels}ch (${stftCache.getNumFrames()} frames cached)`, 'info');
+    viewer = new SpectrogramViewer(canvas, audioBuffer, stftCache);
+    editor.setViewer(viewer);
+    viewer.onPartialSelect = (i) => editor.onPartialSelect(i);
+    viewer.onRender        = ()  => editor.onRender();
+    if (label.startsWith('Test WAV')) validateTestWAVPeaks(stftCache);
+  }, 10);
+}
+
+// File chooser button
+chooseFileBtn.addEventListener('click', () => wavFile.click());
+
+// Load WAV file
+wavFile.addEventListener('change', async (e) => {
+  const file = e.target.files[0];
+  if (!file) return;
+
+  fileLabel.textContent = file.name;
+  setStatus('Loading WAV...', 'info');
+  try {
+    const arrayBuffer = await file.arrayBuffer();
+    const ctx = new AudioContext();
+    const buf = await ctx.decodeAudioData(arrayBuffer);
+    loadAudioBuffer(buf, `Loaded: ${file.name}`);
+  } catch (err) {
+    setStatus('Error loading WAV: ' + err.message, 'error');
+    console.error(err);
+  }
+});
+
+// Test WAV: generate synthetic signal (two sine waves) in-memory
+document.getElementById('testWavBtn').addEventListener('click', () => {
+  initAudioContext();
+  const SR = 32000;
+  const duration = 2.0;
+  const numSamples = SR * duration;
+
+  // Two sine waves: 440 Hz (A4) + 660 Hz (E5, perfect fifth), equal amplitude
+  const buf = audioContext.createBuffer(1, numSamples, SR);
+  const data = buf.getChannelData(0);
+  for (let i = 0; i < numSamples; ++i) {
+    data[i] = 0.5 * Math.sin(2 * Math.PI * 440 * i / SR)
+            + 0.5 * Math.sin(2 * Math.PI * 660 * i / SR);
+  }
+
+  fileLabel.textContent = 'test-440+660hz.wav';
+  loadAudioBuffer(buf, 'Test WAV: 440Hz + 660Hz (2s, 32kHz)');
+});
+
+// Update cache when hop size changes
+hopSize.addEventListener('change', () => {
+  const val = Math.max(64, parseInt(hopSize.value) || 64);
+  hopSize.value = val;
+  if (stftCache) {
+    setStatus('Updating STFT cache...', 'info');
+    setTimeout(() => {
+      stftCache.setHopSize(val);
+      setStatus(`Cache updated (${stftCache.getNumFrames()} frames)`, 'info');
+      if (viewer) viewer.render();
+    }, 10);
+  }
+});
+
+function runExtraction() {
+  if (!stftCache) return;
+
+  setStatus('Extracting partials...', 'info');
+  extractBtn.disabled = true;
+
+  setTimeout(() => {
+    try {
+      const params = {
+        fftSize: fftSize,
+        hopSize: parseInt(hopSize.value),
+        threshold: parseFloat(threshold.value),
+        prominence: parseFloat(prominence.value),
+        freqWeight: freqWeightCb.checked,
+        birthPersistence: parseInt(birthPersistenceEl.value),
+        deathAge: parseInt(deathAgeEl.value),
+        phaseErrorWeight: parseFloat(phaseErrorWeightEl.value),
+        minLength: parseInt(minLengthEl.value),
+        sampleRate: audioBuffer.sampleRate
+      };
+
+      const result = extractPartials(params, stftCache);
+
+      // Sort by decreasing peak amplitude
+      result.partials.sort((a, b) => {
+        const peakA = a.amps.reduce((m, v) => Math.max(m, v), 0);
+        const peakB = b.amps.reduce((m, v) => Math.max(m, v), 0);
+        return peakB - peakA;
+      });
+
+      extractedPartials = result.partials;
+      editor.setPartials(result.partials);
+      viewer.setFrames(result.frames);
+      setStatus(`Extracted ${result.partials.length} partials`, 'info');
+      viewer.setPartials(result.partials);
+      viewer.setKeepCount(getKeepCount());
+      viewer.selectPartial(-1);
+
+    } catch (err) {
+      setStatus('Extraction error: ' + err.message, 'error');
+      console.error(err);
+    }
+    extractBtn.disabled = false;
+    autoSpreadAllBtn.disabled = false;
+  }, 50);
+}
+
+extractBtn.addEventListener('click', () => {
+  if (!audioBuffer) return;
+  runExtraction();
+});
+
+autoSpreadAllBtn.addEventListener('click', () => {
+  if (!extractedPartials || !stftCache) return;
+  const fs = stftCache.fftSize;
+  const sr = audioBuffer.sampleRate;
+  const defaults = { decay_alpha: 0.1, jitter: 0.05, spread_above: 0.02, spread_below: 0.02 };
+  for (const p of extractedPartials) {
+    const {spread_above, spread_below} = autodetectSpread(p, stftCache, fs, sr);
+    if (!p.replicas) p.replicas = { ...defaults };
+    p.replicas.spread_above = spread_above;
+    p.replicas.spread_below = spread_below;
+  }
+  if (viewer) viewer.render();
+  const sel = viewer ? viewer.selectedPartial : -1;
+  if (sel >= 0) editor.onPartialSelect(sel);
+  setStatus(`Auto-spread applied to ${extractedPartials.length} partials`, 'info');
+});
+
+threshold.addEventListener('change', () => {
+  if (stftCache) runExtraction();
+});
+
+freqWeightCb.addEventListener('change', () => {
+  if (stftCache) runExtraction();
+});
+
+for (const el of [birthPersistenceEl, deathAgeEl, phaseErrorWeightEl, minLengthEl]) {
+  el.addEventListener('change', () => { if (stftCache) runExtraction(); });
+}
+
+function playAudioBuffer(buffer, statusMsg) {
+  const startTime = audioContext.currentTime;
+  currentSource = audioContext.createBufferSource();
+  currentSource.buffer = buffer;
+  currentSource.connect(audioContext.destination);
+  currentSource.start();
+  currentSource.onended = () => {
+    currentSource = null;
+    playBtn.disabled = false;
+    stopBtn.disabled = true;
+    viewer.setPlayheadTime(-1);
+    setStatus('Stopped', 'info');
+  };
+  playBtn.disabled = true;
+  stopBtn.disabled = false;
+  setStatus(statusMsg, 'info');
+  function tick() {
+    if (!currentSource) return;
+    viewer.setPlayheadTime(audioContext.currentTime - startTime);
+    requestAnimationFrame(tick);
+  }
+  tick();
+}
+
+function stopAudio() {
+  if (currentSource) {
+    try { currentSource.stop(); } catch (e) {}
+    currentSource = null;
+  }
+  if (viewer) viewer.setPlayheadTime(-1);
+  playBtn.disabled = false;
+  stopBtn.disabled = true;
+  setStatus('Stopped', 'info');
+}
+
+// Play audio
+playBtn.addEventListener('click', () => {
+  if (!audioBuffer || !audioContext) return;
+  stopAudio();
+  playAudioBuffer(audioBuffer, 'Playing...');
+});
+
+// Stop audio
+stopBtn.addEventListener('click', () => {
+  stopAudio();
+});
+
+function setStatus(msg, type = '') {
+  status.innerHTML = msg;
+  status.className = type;
+}
+
+// Play synthesized audio
+function playSynthesized() {
+  if (!extractedPartials || extractedPartials.length === 0) {
+    setStatus('No partials extracted yet', 'warn');
+    return;
+  }
+  if (!audioBuffer || !audioContext) return;
+
+  stopAudio();
+
+  setStatus('Synthesizing...', 'info');
+
+  const keepCount = getKeepCount();
+  const partialsToUse = extractedPartials.slice(0, keepCount).filter(p => !p.muted);
+  setStatus(`Synthesizing ${partialsToUse.length}/${extractedPartials.length} partials (${keepPct.value}%)...`, 'info');
+
+  const integratePhase  = document.getElementById('integratePhase').checked;
+  const disableJitter   = document.getElementById('disableJitter').checked;
+  const disableSpread   = document.getElementById('disableSpread').checked;
+  const forceResonator  = document.getElementById('forceResonator').checked;
+  const lpK1Raw = parseFloat(document.getElementById('lpK1').value);
+  const hpK2Raw = parseFloat(document.getElementById('hpK2').value);
+  const k1 = lpK1Raw < 1.0 ? lpK1Raw : null;
+  const k2 = hpK2Raw < 1.0 ? hpK2Raw : null;
+  const forceRGain   = forceResonator && document.getElementById('forceRGain').checked;
+  const globalR      = parseFloat(document.getElementById('globalR').value);
+  const globalGain   = parseFloat(document.getElementById('globalGain').value);
+  const pcm = synthesizeMQ(partialsToUse, audioBuffer.sampleRate, audioBuffer.duration,
+                           integratePhase, {disableJitter, disableSpread, forceResonator,
+                                            forceRGain, globalR, globalGain, k1, k2});
+
+  if (viewer) {
+    viewer.setSynthStftCache(new STFTCache(pcm, audioBuffer.sampleRate, fftSize, parseInt(hopSize.value)));
+  }
+
+  const synthBuffer = audioContext.createBuffer(1, pcm.length, audioBuffer.sampleRate);
+  synthBuffer.getChannelData(0).set(pcm);
+  playAudioBuffer(synthBuffer, `Playing synthesized (${partialsToUse.length}/${extractedPartials.length} partials, ${keepPct.value}%)...`);
+}
+
+// Keyboard shortcuts
+document.addEventListener('keydown', (e) => {
+  if (e.target.tagName === 'INPUT' || e.target.tagName === 'TEXTAREA') return;
+  if (e.code === 'Digit1') {
+    e.preventDefault();
+    playSynthesized();
+  } else if (e.code === 'Digit2') {
+    e.preventDefault();
+    if (!playBtn.disabled) {
+      playBtn.click();
+    }
+  } else if (e.code === 'KeyP') {
+    e.preventDefault();
+    if (viewer) viewer.togglePeaks();
+  } else if (e.code === 'KeyA') {
+    e.preventDefault();
+    if (viewer) {
+      viewer.showSynthFFT = !viewer.showSynthFFT;
+      viewer.renderSpectrum();
+    }
+  } else if (e.code === 'KeyE') {
+    e.preventDefault();
+    if (!extractBtn.disabled) extractBtn.click();
+  } else if (e.code === 'Escape') {
+    if (viewer) viewer.selectPartial(-1);
+  }
+});
+
+// Curve tab switching
+document.querySelectorAll('.tab-btn').forEach(btn => {
+  btn.addEventListener('click', () => {
+    document.querySelectorAll('.tab-btn').forEach(b => b.classList.remove('active'));
+    btn.classList.add('active');
+    document.querySelectorAll('.tab-pane').forEach(p => p.style.display = 'none');
+    document.getElementById('tab' + btn.dataset.tab).style.display = '';
+  });
+});
+
+// --- Test WAV peak validation ---
+function validateTestWAVPeaks(cache) {
+  const SR = cache.sampleRate;
+  const N = cache.fftSize;
+  const binWidth = SR / N;  // Hz per bin
+  const numBins = N / 2;
+  const numBars = 100;      // mini-spectrum bar count
+
+  // Use a mid-signal frame (avoid edge effects)
+  const midFrame = cache.frames[Math.floor(cache.frames.length / 2)];
+  if (!midFrame) { console.error('[TestWAV] No frames computed'); return; }
+  const sq = midFrame.squaredAmplitude;
+  const t = midFrame.time;
+
+  console.group('[TestWAV] Peak validation @ t=' + t.toFixed(3) + 's');
+
+  // Top 5 bins by magnitude
+  const ranked = Array.from(sq)
+    .map((v, i) => ({ bin: i, freq: i * binWidth, db: 10 * Math.log10(Math.max(v, 1e-20)) }))
+    .sort((a, b) => b.db - a.db);
+  console.log('Top 5 FFT bins:');
+  ranked.slice(0, 5).forEach(x =>
+    console.log(`  bin ${x.bin.toString().padStart(3)}: ${x.freq.toFixed(1).padStart(7)}Hz  ${x.db.toFixed(1)}dB`));
+
+  // Expected bins for 440/660 Hz
+  const bin440 = Math.round(440 / binWidth);
+  const bin660 = Math.round(660 / binWidth);
+  const db440 = 10 * Math.log10(Math.max(sq[bin440], 1e-20));
+  const db660 = 10 * Math.log10(Math.max(sq[bin660], 1e-20));
+  console.log(`440Hz → bin ${bin440} (${(bin440 * binWidth).toFixed(1)}Hz): ${db440.toFixed(1)}dB`);
+  console.log(`660Hz → bin ${bin660} (${(bin660 * binWidth).toFixed(1)}Hz): ${db660.toFixed(1)}dB`);
+
+  // Validate: 440/660 Hz must be in top-10
+  const top10Freqs = ranked.slice(0, 10).map(x => x.freq);
+  const pass440 = top10Freqs.some(f => Math.abs(f - 440) < binWidth * 2);
+  const pass660 = top10Freqs.some(f => Math.abs(f - 660) < binWidth * 2);
+  console.log('Peak check: 440Hz ' + (pass440 ? 'PASS ✓' : 'FAIL ✗') +
+              ',  660Hz ' + (pass660 ? 'PASS ✓' : 'FAIL ✗'));
+
+  // Mini-spectrum: which bar do these peaks land in?
+  const bar440 = Math.floor(bin440 * numBars / numBins);
+  const bar660 = Math.floor(bin660 * numBars / numBins);
+  const sampledBin440 = Math.floor(bar440 * numBins / numBars);
+  const sampledBin660 = Math.floor(bar660 * numBars / numBars);
+  console.log('Mini-spectrum (linear scale, 100 bars):');
+  console.log(`  440Hz (bin ${bin440}) → bar ${bar440}/100  [bar samples bin ${sampledBin440} = ${(sampledBin440 * binWidth).toFixed(1)}Hz]`);
+  console.log(`  660Hz (bin ${bin660}) → bar ${bar660}/100  [bar samples bin ${Math.floor(bar660 * numBins / numBars)} = ${(Math.floor(bar660 * numBins / numBars) * binWidth).toFixed(1)}Hz]`);
+  if (bar440 < 5 || bar660 < 5) {
+    console.warn('  ⚠ BUG: peaks fall in bars ' + bar440 + ' and ' + bar660 +
+                 ' (leftmost ~' + Math.max(bar440, bar660) * 2 + 'px of 200px canvas)' +
+                 ' — linear scale hides low-frequency peaks. Need log-scale bar mapping.');
+  }
+
+  // Main spectrogram: confirm bins are in draw range
+  const mainFreqStart = 20, mainFreqEnd = 16000;
+  const inRange440 = 440 >= mainFreqStart && 440 <= mainFreqEnd;
+  const inRange660 = 660 >= mainFreqStart && 660 <= mainFreqEnd;
+  const norm440 = (Math.log2(440) - Math.log2(mainFreqStart)) / (Math.log2(mainFreqEnd) - Math.log2(mainFreqStart));
+  const norm660 = (Math.log2(660) - Math.log2(mainFreqStart)) / (Math.log2(mainFreqEnd) - Math.log2(mainFreqStart));
+  console.log('Main spectrogram (log Y-axis, 600px):');
+  console.log(`  440Hz: in range=${inRange440}, y=${Math.round(600 * (1 - norm440))}px, db=${db440.toFixed(1)}dB → intensity=${Math.min(1, Math.pow(Math.max(0, (db440 + 80) / 80), 2)).toFixed(2)}`);
+  console.log(`  660Hz: in range=${inRange660}, y=${Math.round(600 * (1 - norm660))}px, db=${db660.toFixed(1)}dB → intensity=${Math.min(1, Math.pow(Math.max(0, (db660 + 80) / 80), 2)).toFixed(2)}`);
+
+  console.groupEnd();
+}
diff --git a/tools/mq_editor/editor.js b/tools/mq_editor/editor.js
index 97d8a7a..301dcc5 100644
--- a/tools/mq_editor/editor.js
+++ b/tools/mq_editor/editor.js
@@ -181,7 +181,15 @@ class PartialEditor {
       });
       sinInputs[p.key] = inp;
 
-      const jog = this._makeJogSlider(inp, partial, index, p, repDefaults);
+      const jog = this._makeJogSlider(inp, {
+        step: parseFloat(p.step),
+        onUpdate: (newVal) => {
+          if (!this.partials || !this.partials[index]) return;
+          if (!this.partials[index].replicas) this.partials[index].replicas = { ...repDefaults };
+          this.partials[index].replicas[p.key] = newVal;
+          if (this.viewer) this.viewer.render();
+        }
+      });
       const wrap = document.createElement('div');
       wrap.className = 'synth-field-wrap';
       wrap.appendChild(inp);
@@ -245,45 +253,15 @@ class PartialEditor {
         if (this.viewer) this.viewer.render();
       });
 
-      // Inline jog slider for resonator params
-      const step = parseFloat(p.step);
-      const sensitivity = step * 5;
-      const jog = document.createElement('div');
-      jog.className = 'jog-slider';
-      const thumb = document.createElement('div');
-      thumb.className = 'jog-thumb';
-      jog.appendChild(thumb);
-      let dragging = false, startX = 0, startVal = 0;
-      const onMove = (ev) => {
-        if (!dragging) return;
-        const dx = ev.clientX - startX;
-        const half = jog.offsetWidth / 2;
-        const clamped = Math.max(-half, Math.min(half, dx));
-        thumb.style.transition = 'none';
-        thumb.style.left = `calc(50% - 3px + ${clamped}px)`;
-        const newVal = Math.max(parseFloat(inp.min) || 0,
-                        Math.min(parseFloat(inp.max) || 1e9, startVal + dx * sensitivity));
-        inp.value = newVal.toFixed(4);
-        if (!this.partials || !this.partials[index]) return;
-        if (!this.partials[index].resonator) this.partials[index].resonator = { ...resDefaults };
-        this.partials[index].resonator[p.key] = newVal;
-        if (this.viewer) this.viewer.render();
-      };
-      const onUp = () => {
-        if (!dragging) return;
-        dragging = false;
-        thumb.style.transition = '';
-        thumb.style.left = 'calc(50% - 3px)';
-        document.removeEventListener('mousemove', onMove);
-        document.removeEventListener('mouseup', onUp);
-      };
-      jog.addEventListener('mousedown', (ev) => {
-        dragging = true;
-        startX   = ev.clientX;
-        startVal = parseFloat(inp.value) || 0;
-        document.addEventListener('mousemove', onMove);
-        document.addEventListener('mouseup', onUp);
-        ev.preventDefault();
+      const jog = this._makeJogSlider(inp, {
+        step: parseFloat(p.step),
+        decimals: 4,
+        onUpdate: (newVal) => {
+          if (!this.partials || !this.partials[index]) return;
+          if (!this.partials[index].resonator) this.partials[index].resonator = { ...resDefaults };
+          this.partials[index].resonator[p.key] = newVal;
+          if (this.viewer) this.viewer.render();
+        }
       });
 
       const wrap = document.createElement('div');
@@ -322,14 +300,20 @@ class PartialEditor {
     });
   }
 
-  _makeJogSlider(inp, partial, index, p, defaults) {
+  _makeJogSlider(inp, options) {
+    const {step, onUpdate, decimals = 3} = options;
+    const min = options.min != null ? options.min :
+                (inp.min !== '' && !isNaN(parseFloat(inp.min)) ? parseFloat(inp.min) : 0);
+    const max = options.max != null ? options.max :
+                (inp.max !== '' && !isNaN(parseFloat(inp.max)) ? parseFloat(inp.max) : Infinity);
+    const sensitivity = step * 5;
+
     const slider = document.createElement('div');
     slider.className = 'jog-slider';
     const thumb = document.createElement('div');
     thumb.className = 'jog-thumb';
     slider.appendChild(thumb);
 
-    const sensitivity = parseFloat(p.step) * 5;
     let startX = 0, startVal = 0, dragging = false;
 
     const onMove = (e) => {
@@ -339,12 +323,9 @@ class PartialEditor {
       const clamped = Math.max(-half, Math.min(half, dx));
       thumb.style.transition = 'none';
       thumb.style.left = `calc(50% - 3px + ${clamped}px)`;
-      const newVal = Math.max(0, startVal + dx * sensitivity);
-      inp.value = newVal.toFixed(3);
-      if (!this.partials || !this.partials[index]) return;
-      if (!this.partials[index].replicas) this.partials[index].replicas = { ...defaults };
-      this.partials[index].replicas[p.key] = newVal;
-      if (this.viewer) this.viewer.render();
+      const newVal = Math.max(min, Math.min(max, startVal + dx * sensitivity));
+      inp.value = newVal.toFixed(decimals);
+      onUpdate(newVal);
     };
 
     const onUp = () => {
@@ -359,7 +340,7 @@ class PartialEditor {
     slider.addEventListener('mousedown', (e) => {
       dragging = true;
       startX   = e.clientX;
-      startVal = Math.max(0, parseFloat(inp.value) || 0);
+      startVal = Math.max(min, parseFloat(inp.value) || 0);
       document.addEventListener('mousemove', onMove);
       document.addEventListener('mouseup', onUp);
       e.preventDefault();
@@ -504,8 +485,7 @@ class PartialEditor {
       if (this._selectedIndex < 0 || !this.partials) return;
       const partial = this.partials[this._selectedIndex];
       if (!partial || !partial.ampCurve) return;
-      const rect  = canvas.getBoundingClientRect();
-      const x = e.clientX - rect.left, y = e.clientY - rect.top;
+      const {x, y} = getCanvasCoords(e, canvas);
       const curve = partial.ampCurve;
       for (let i = 0; i < 4; ++i) {
         if (Math.hypot(this._tToX(curve['t' + i]) - x, this._ampToY(curve['v' + i]) - y) <= 8) {
@@ -518,8 +498,7 @@ class PartialEditor {
     });
 
     canvas.addEventListener('mousemove', (e) => {
-      const rect  = canvas.getBoundingClientRect();
-      const x = e.clientX - rect.left, y = e.clientY - rect.top;
+      const {x, y} = getCanvasCoords(e, canvas);
 
       if (this._dragPointIndex >= 0) {
         const curve = this.partials[this._selectedIndex].ampCurve;
diff --git a/tools/mq_editor/index.html b/tools/mq_editor/index.html
index 5f6af24..4737d67 100644
--- a/tools/mq_editor/index.html
+++ b/tools/mq_editor/index.html
@@ -424,457 +424,12 @@
 
   <div id="status">Load a WAV file to begin...</div>
 
+  <script src="utils.js"></script>
   <script src="fft.js"></script>
   <script src="mq_extract.js"></script>
   <script src="mq_synth.js"></script>
   <script src="viewer.js"></script>
   <script src="editor.js"></script>
-  <script>
-    // LP: y[n] = k*x[n] + (1-k)*y[n-1]  => -3dB at cos(w) = (2-2k-k²)/(2(1-k))
-    function k1ToHz(k, sr) {
-      if (k >= 1.0) return sr / 2;
-      const cosW = (2 - 2*k - k*k) / (2*(1 - k));
-      return Math.acos(Math.max(-1, Math.min(1, cosW))) * sr / (2 * Math.PI);
-    }
-    // HP: y[n] = k*(y[n-1]+x[n]-x[n-1])  => -3dB from peak at cos(w) = 2k/(1+k²)
-    function k2ToHz(k, sr) {
-      if (k >= 1.0) return 0;
-      const cosW = 2*k / (1 + k*k);
-      return Math.acos(Math.max(-1, Math.min(1, cosW))) * sr / (2 * Math.PI);
-    }
-    function fmtHz(f) {
-      return f >= 1000 ? (f/1000).toFixed(1) + 'k' : Math.round(f) + 'Hz';
-    }
-    function getSR() { return (typeof audioBuffer !== 'undefined' && audioBuffer) ? audioBuffer.sampleRate : 44100; }
-
-    // LP/HP slider live display
-    document.getElementById('lpK1').addEventListener('input', function() {
-      const k = parseFloat(this.value);
-      const f = k1ToHz(k, getSR());
-      document.getElementById('lpK1Val').textContent = k >= 1.0 ? 'bypass' : fmtHz(f);
-    });
-    document.getElementById('hpK2').addEventListener('input', function() {
-      const k = parseFloat(this.value);
-      const f = k2ToHz(k, getSR());
-      document.getElementById('hpK2Val').textContent = k >= 1.0 ? 'bypass' : fmtHz(f);
-    });
-
-    // Show/hide global resonator params when forceResonator toggled
-    document.getElementById('forceResonator').addEventListener('change', function() {
-      document.getElementById('globalResParams').style.display = this.checked ? '' : 'none';
-    });
-    document.getElementById('globalR').addEventListener('input', function() {
-      document.getElementById('globalRVal').textContent = parseFloat(this.value).toFixed(4);
-    });
-    document.getElementById('globalGain').addEventListener('input', function() {
-      document.getElementById('globalGainVal').textContent = parseFloat(this.value).toFixed(2);
-    });
-    let audioBuffer = null;
-    let viewer = null;
-    let audioContext = null;
-    let currentSource = null;
-    let extractedPartials = null;
-    let stftCache = null;
-
-    const wavFile = document.getElementById('wavFile');
-    const chooseFileBtn = document.getElementById('chooseFileBtn');
-    const extractBtn = document.getElementById('extractBtn');
-    const autoSpreadAllBtn = document.getElementById('autoSpreadAllBtn');
-    const playBtn = document.getElementById('playBtn');
-    const stopBtn = document.getElementById('stopBtn');
-    const canvas = document.getElementById('canvas');
-    const status = document.getElementById('status');
-    const fileLabel = document.getElementById('fileLabel');
-
-    const hopSize = document.getElementById('hopSize');
-    const threshold = document.getElementById('threshold');
-    const prominence = document.getElementById('prominence');
-    const freqWeightCb = document.getElementById('freqWeight');
-    const birthPersistenceEl = document.getElementById('birthPersistence');
-    const deathAgeEl = document.getElementById('deathAge');
-    const phaseErrorWeightEl = document.getElementById('phaseErrorWeight');
-    const minLengthEl = document.getElementById('minLength');
-    const keepPct = document.getElementById('keepPct');
-    const keepPctLabel = document.getElementById('keepPctLabel');
-    const fftSize = 1024; // Fixed
-
-    function getKeepCount() {
-      return Math.max(1, Math.ceil(extractedPartials.length * parseInt(keepPct.value) / 100));
-    }
-
-    keepPct.addEventListener('input', () => {
-      keepPctLabel.textContent = keepPct.value + '%';
-      if (viewer && extractedPartials) viewer.setKeepCount(getKeepCount());
-    });
-
-    // --- Editor ---
-    const editor = new PartialEditor();
-    editor.onPartialDeleted = () => {
-      if (viewer && extractedPartials)
-        viewer.setKeepCount(extractedPartials.length > 0 ? getKeepCount() : 0);
-    };
-
-    // Initialize audio context
-    function initAudioContext() {
-      if (!audioContext) {
-        audioContext = new (window.AudioContext || window.webkitAudioContext)();
-      }
-    }
-
-    // Shared: initialize editor from an AudioBuffer
-    function loadAudioBuffer(buffer, label) {
-      audioBuffer = buffer;
-      initAudioContext();
-      extractBtn.disabled = false;
-      playBtn.disabled = false;
-      setStatus('Computing STFT cache...', 'info');
-
-      // Reset partials from previous file
-      extractedPartials = null;
-      editor.setPartials(null);
-
-      setTimeout(() => {
-        const signal = audioBuffer.getChannelData(0);
-        stftCache = new STFTCache(signal, audioBuffer.sampleRate, fftSize, Math.max(64, parseInt(hopSize.value) || 64));
-        setStatus(`${label} — ${audioBuffer.duration.toFixed(2)}s, ${audioBuffer.sampleRate}Hz, ${audioBuffer.numberOfChannels}ch (${stftCache.getNumFrames()} frames cached)`, 'info');
-        viewer = new SpectrogramViewer(canvas, audioBuffer, stftCache);
-        editor.setViewer(viewer);
-        viewer.onPartialSelect = (i) => editor.onPartialSelect(i);
-        viewer.onRender        = ()  => editor.onRender();
-        if (label.startsWith('Test WAV')) validateTestWAVPeaks(stftCache);
-      }, 10);
-    }
-
-    // File chooser button
-    chooseFileBtn.addEventListener('click', () => wavFile.click());
-
-    // Load WAV file
-    wavFile.addEventListener('change', async (e) => {
-      const file = e.target.files[0];
-      if (!file) return;
-
-      fileLabel.textContent = file.name;
-      setStatus('Loading WAV...', 'info');
-      try {
-        const arrayBuffer = await file.arrayBuffer();
-        const ctx = new AudioContext();
-        const buf = await ctx.decodeAudioData(arrayBuffer);
-        loadAudioBuffer(buf, `Loaded: ${file.name}`);
-      } catch (err) {
-        setStatus('Error loading WAV: ' + err.message, 'error');
-        console.error(err);
-      }
-    });
-
-    // Test WAV: generate synthetic signal (two sine waves) in-memory
-    document.getElementById('testWavBtn').addEventListener('click', () => {
-      initAudioContext();
-      const SR = 32000;
-      const duration = 2.0;
-      const numSamples = SR * duration;
-
-      // Two sine waves: 440 Hz (A4) + 660 Hz (E5, perfect fifth), equal amplitude
-      const buf = audioContext.createBuffer(1, numSamples, SR);
-      const data = buf.getChannelData(0);
-      for (let i = 0; i < numSamples; ++i) {
-        data[i] = 0.5 * Math.sin(2 * Math.PI * 440 * i / SR)
-                + 0.5 * Math.sin(2 * Math.PI * 660 * i / SR);
-      }
-
-      fileLabel.textContent = 'test-440+660hz.wav';
-      loadAudioBuffer(buf, 'Test WAV: 440Hz + 660Hz (2s, 32kHz)');
-    });
-
-    // Update cache when hop size changes
-    hopSize.addEventListener('change', () => {
-      const val = Math.max(64, parseInt(hopSize.value) || 64);
-      hopSize.value = val;
-      if (stftCache) {
-        setStatus('Updating STFT cache...', 'info');
-        setTimeout(() => {
-          stftCache.setHopSize(val);
-          setStatus(`Cache updated (${stftCache.getNumFrames()} frames)`, 'info');
-          if (viewer) viewer.render();
-        }, 10);
-      }
-    });
-
-    function runExtraction() {
-      if (!stftCache) return;
-
-      setStatus('Extracting partials...', 'info');
-      extractBtn.disabled = true;
-
-      setTimeout(() => {
-        try {
-          const params = {
-            fftSize: fftSize,
-            hopSize: parseInt(hopSize.value),
-            threshold: parseFloat(threshold.value),
-            prominence: parseFloat(prominence.value),
-            freqWeight: freqWeightCb.checked,
-            birthPersistence: parseInt(birthPersistenceEl.value),
-            deathAge: parseInt(deathAgeEl.value),
-            phaseErrorWeight: parseFloat(phaseErrorWeightEl.value),
-            minLength: parseInt(minLengthEl.value),
-            sampleRate: audioBuffer.sampleRate
-          };
-
-          const result = extractPartials(params, stftCache);
-
-          // Sort by decreasing peak amplitude
-          result.partials.sort((a, b) => {
-            const peakA = a.amps.reduce((m, v) => Math.max(m, v), 0);
-            const peakB = b.amps.reduce((m, v) => Math.max(m, v), 0);
-            return peakB - peakA;
-          });
-
-          extractedPartials = result.partials;
-          editor.setPartials(result.partials);
-          viewer.setFrames(result.frames);
-          setStatus(`Extracted ${result.partials.length} partials`, 'info');
-          viewer.setPartials(result.partials);
-          viewer.setKeepCount(getKeepCount());
-          viewer.selectPartial(-1);
-
-        } catch (err) {
-          setStatus('Extraction error: ' + err.message, 'error');
-          console.error(err);
-        }
-        extractBtn.disabled = false;
-        autoSpreadAllBtn.disabled = false;
-      }, 50);
-    }
-
-    extractBtn.addEventListener('click', () => {
-      if (!audioBuffer) return;
-      runExtraction();
-    });
-
-    autoSpreadAllBtn.addEventListener('click', () => {
-      if (!extractedPartials || !stftCache) return;
-      const fs = stftCache.fftSize;
-      const sr = audioBuffer.sampleRate;
-      const defaults = { decay_alpha: 0.1, jitter: 0.05, spread_above: 0.02, spread_below: 0.02 };
-      for (const p of extractedPartials) {
-        const {spread_above, spread_below} = autodetectSpread(p, stftCache, fs, sr);
-        if (!p.replicas) p.replicas = { ...defaults };
-        p.replicas.spread_above = spread_above;
-        p.replicas.spread_below = spread_below;
-      }
-      if (viewer) viewer.render();
-      const sel = viewer ? viewer.selectedPartial : -1;
-      if (sel >= 0) editor.onPartialSelect(sel);
-      setStatus(`Auto-spread applied to ${extractedPartials.length} partials`, 'info');
-    });
-
-    threshold.addEventListener('change', () => {
-      if (stftCache) runExtraction();
-    });
-
-    freqWeightCb.addEventListener('change', () => {
-      if (stftCache) runExtraction();
-    });
-
-    for (const el of [birthPersistenceEl, deathAgeEl, phaseErrorWeightEl, minLengthEl]) {
-      el.addEventListener('change', () => { if (stftCache) runExtraction(); });
-    }
-
-    function playAudioBuffer(buffer, statusMsg) {
-      const startTime = audioContext.currentTime;
-      currentSource = audioContext.createBufferSource();
-      currentSource.buffer = buffer;
-      currentSource.connect(audioContext.destination);
-      currentSource.start();
-      currentSource.onended = () => {
-        currentSource = null;
-        playBtn.disabled = false;
-        stopBtn.disabled = true;
-        viewer.setPlayheadTime(-1);
-        setStatus('Stopped', 'info');
-      };
-      playBtn.disabled = true;
-      stopBtn.disabled = false;
-      setStatus(statusMsg, 'info');
-      function tick() {
-        if (!currentSource) return;
-        viewer.setPlayheadTime(audioContext.currentTime - startTime);
-        requestAnimationFrame(tick);
-      }
-      tick();
-    }
-
-    function stopAudio() {
-      if (currentSource) {
-        try { currentSource.stop(); } catch (e) {}
-        currentSource = null;
-      }
-      if (viewer) viewer.setPlayheadTime(-1);
-      playBtn.disabled = false;
-      stopBtn.disabled = true;
-      setStatus('Stopped', 'info');
-    }
-
-    // Play audio
-    playBtn.addEventListener('click', () => {
-      if (!audioBuffer || !audioContext) return;
-      stopAudio();
-      playAudioBuffer(audioBuffer, 'Playing...');
-    });
-
-    // Stop audio
-    stopBtn.addEventListener('click', () => {
-      stopAudio();
-    });
-
-    function setStatus(msg, type = '') {
-      status.innerHTML = msg;
-      status.className = type;
-    }
-
-    // Play synthesized audio
-    function playSynthesized() {
-      if (!extractedPartials || extractedPartials.length === 0) {
-        setStatus('No partials extracted yet', 'warn');
-        return;
-      }
-      if (!audioBuffer || !audioContext) return;
-
-      stopAudio();
-
-      setStatus('Synthesizing...', 'info');
-
-      const keepCount = getKeepCount();
-      const partialsToUse = extractedPartials.slice(0, keepCount).filter(p => !p.muted);
-      setStatus(`Synthesizing ${partialsToUse.length}/${extractedPartials.length} partials (${keepPct.value}%)...`, 'info');
-
-      const integratePhase  = document.getElementById('integratePhase').checked;
-      const disableJitter   = document.getElementById('disableJitter').checked;
-      const disableSpread   = document.getElementById('disableSpread').checked;
-      const forceResonator  = document.getElementById('forceResonator').checked;
-      const lpK1Raw = parseFloat(document.getElementById('lpK1').value);
-      const hpK2Raw = parseFloat(document.getElementById('hpK2').value);
-      const k1 = lpK1Raw < 1.0 ? lpK1Raw : null;
-      const k2 = hpK2Raw < 1.0 ? hpK2Raw : null;
-      const forceRGain   = forceResonator && document.getElementById('forceRGain').checked;
-      const globalR      = parseFloat(document.getElementById('globalR').value);
-      const globalGain   = parseFloat(document.getElementById('globalGain').value);
-      const pcm = synthesizeMQ(partialsToUse, audioBuffer.sampleRate, audioBuffer.duration,
-                               integratePhase, {disableJitter, disableSpread, forceResonator,
-                                                forceRGain, globalR, globalGain, k1, k2});
-
-      if (viewer) {
-        viewer.setSynthStftCache(new STFTCache(pcm, audioBuffer.sampleRate, fftSize, parseInt(hopSize.value)));
-      }
-
-      const synthBuffer = audioContext.createBuffer(1, pcm.length, audioBuffer.sampleRate);
-      synthBuffer.getChannelData(0).set(pcm);
-      playAudioBuffer(synthBuffer, `Playing synthesized (${partialsToUse.length}/${extractedPartials.length} partials, ${keepPct.value}%)...`);
-    }
-
-    // Keyboard shortcuts
-    document.addEventListener('keydown', (e) => {
-      if (e.target.tagName === 'INPUT' || e.target.tagName === 'TEXTAREA') return;
-      if (e.code === 'Digit1') {
-        e.preventDefault();
-        playSynthesized();
-      } else if (e.code === 'Digit2') {
-        e.preventDefault();
-        if (!playBtn.disabled) {
-          playBtn.click();
-        }
-      } else if (e.code === 'KeyP') {
-        e.preventDefault();
-        if (viewer) viewer.togglePeaks();
-      } else if (e.code === 'KeyA') {
-        e.preventDefault();
-        if (viewer) {
-          viewer.showSynthFFT = !viewer.showSynthFFT;
-          viewer.renderSpectrum();
-        }
-      } else if (e.code === 'KeyE') {
-        e.preventDefault();
-        if (!extractBtn.disabled) extractBtn.click();
-      } else if (e.code === 'Escape') {
-        if (viewer) viewer.selectPartial(-1);
-      }
-    });
-
-    // Curve tab switching
-    document.querySelectorAll('.tab-btn').forEach(btn => {
-      btn.addEventListener('click', () => {
-        document.querySelectorAll('.tab-btn').forEach(b => b.classList.remove('active'));
-        btn.classList.add('active');
-        document.querySelectorAll('.tab-pane').forEach(p => p.style.display = 'none');
-        document.getElementById('tab' + btn.dataset.tab).style.display = '';
-      });
-    });
-
-    // --- Test WAV peak validation ---
-    function validateTestWAVPeaks(cache) {
-      const SR = cache.sampleRate;
-      const N = cache.fftSize;
-      const binWidth = SR / N;  // Hz per bin
-      const numBins = N / 2;
-      const numBars = 100;      // mini-spectrum bar count
-
-      // Use a mid-signal frame (avoid edge effects)
-      const midFrame = cache.frames[Math.floor(cache.frames.length / 2)];
-      if (!midFrame) { console.error('[TestWAV] No frames computed'); return; }
-      const sq = midFrame.squaredAmplitude;
-      const t = midFrame.time;
-
-      console.group('[TestWAV] Peak validation @ t=' + t.toFixed(3) + 's');
-
-      // Top 5 bins by magnitude
-      const ranked = Array.from(sq)
-        .map((v, i) => ({ bin: i, freq: i * binWidth, db: 10 * Math.log10(Math.max(v, 1e-20)) }))
-        .sort((a, b) => b.db - a.db);
-      console.log('Top 5 FFT bins:');
-      ranked.slice(0, 5).forEach(x =>
-        console.log(`  bin ${x.bin.toString().padStart(3)}: ${x.freq.toFixed(1).padStart(7)}Hz  ${x.db.toFixed(1)}dB`));
-
-      // Expected bins for 440/660 Hz
-      const bin440 = Math.round(440 / binWidth);
-      const bin660 = Math.round(660 / binWidth);
-      const db440 = 10 * Math.log10(Math.max(sq[bin440], 1e-20));
-      const db660 = 10 * Math.log10(Math.max(sq[bin660], 1e-20));
-      console.log(`440Hz → bin ${bin440} (${(bin440 * binWidth).toFixed(1)}Hz): ${db440.toFixed(1)}dB`);
-      console.log(`660Hz → bin ${bin660} (${(bin660 * binWidth).toFixed(1)}Hz): ${db660.toFixed(1)}dB`);
-
-      // Validate: 440/660 Hz must be in top-10
-      const top10Freqs = ranked.slice(0, 10).map(x => x.freq);
-      const pass440 = top10Freqs.some(f => Math.abs(f - 440) < binWidth * 2);
-      const pass660 = top10Freqs.some(f => Math.abs(f - 660) < binWidth * 2);
-      console.log('Peak check: 440Hz ' + (pass440 ? 'PASS ✓' : 'FAIL ✗') +
-                  ',  660Hz ' + (pass660 ? 'PASS ✓' : 'FAIL ✗'));
-
-      // Mini-spectrum: which bar do these peaks land in?
-      const bar440 = Math.floor(bin440 * numBars / numBins);
-      const bar660 = Math.floor(bin660 * numBars / numBins);
-      const sampledBin440 = Math.floor(bar440 * numBins / numBars);
-      const sampledBin660 = Math.floor(bar660 * numBars / numBars);
-      console.log('Mini-spectrum (linear scale, 100 bars):');
-      console.log(`  440Hz (bin ${bin440}) → bar ${bar440}/100  [bar samples bin ${sampledBin440} = ${(sampledBin440 * binWidth).toFixed(1)}Hz]`);
-      console.log(`  660Hz (bin ${bin660}) → bar ${bar660}/100  [bar samples bin ${Math.floor(bar660 * numBins / numBars)} = ${(Math.floor(bar660 * numBins / numBars) * binWidth).toFixed(1)}Hz]`);
-      if (bar440 < 5 || bar660 < 5) {
-        console.warn('  ⚠ BUG: peaks fall in bars ' + bar440 + ' and ' + bar660 +
-                     ' (leftmost ~' + Math.max(bar440, bar660) * 2 + 'px of 200px canvas)' +
-                     ' — linear scale hides low-frequency peaks. Need log-scale bar mapping.');
-      }
-
-      // Main spectrogram: confirm bins are in draw range
-      const mainFreqStart = 20, mainFreqEnd = 16000;
-      const inRange440 = 440 >= mainFreqStart && 440 <= mainFreqEnd;
-      const inRange660 = 660 >= mainFreqStart && 660 <= mainFreqEnd;
-      const norm440 = (Math.log2(440) - Math.log2(mainFreqStart)) / (Math.log2(mainFreqEnd) - Math.log2(mainFreqStart));
-      const norm660 = (Math.log2(660) - Math.log2(mainFreqStart)) / (Math.log2(mainFreqEnd) - Math.log2(mainFreqStart));
-      console.log('Main spectrogram (log Y-axis, 600px):');
-      console.log(`  440Hz: in range=${inRange440}, y=${Math.round(600 * (1 - norm440))}px, db=${db440.toFixed(1)}dB → intensity=${Math.min(1, Math.pow(Math.max(0, (db440 + 80) / 80), 2)).toFixed(2)}`);
-      console.log(`  660Hz: in range=${inRange660}, y=${Math.round(600 * (1 - norm660))}px, db=${db660.toFixed(1)}dB → intensity=${Math.min(1, Math.pow(Math.max(0, (db660 + 80) / 80), 2)).toFixed(2)}`);
-
-      console.groupEnd();
-    }
-  </script>
+  <script src="app.js"></script>
 </body>
 </html>
diff --git a/tools/mq_editor/mq_extract.js b/tools/mq_editor/mq_extract.js
index 3f7490d..107b2ac 100644
--- a/tools/mq_editor/mq_extract.js
+++ b/tools/mq_editor/mq_extract.js
@@ -102,6 +102,21 @@ function normalizeAngle(angle) {
   return angle - 2 * Math.PI * Math.floor((angle + Math.PI) / (2 * Math.PI));
 }
 
+// Find best matching peak for a predicted freq/phase. Returns {bestIdx, bestCost}.
+function findBestPeak(peaks, matched, predictedFreq, predictedPhase, tol, phaseErrorWeight) {
+  let bestIdx = -1, bestCost = Infinity;
+  for (let i = 0; i < peaks.length; ++i) {
+    if (matched.has(i)) continue;
+    const pk = peaks[i];
+    const freqError = Math.abs(pk.freq - predictedFreq);
+    if (freqError > tol) continue;
+    const phaseError = Math.abs(normalizeAngle(pk.phase - predictedPhase));
+    const cost = freqError + phaseErrorWeight * phaseError * predictedFreq;
+    if (cost < bestCost) { bestCost = cost; bestIdx = i; }
+  }
+  return { bestIdx, bestCost };
+}
+
 // Track partials across frames using phase coherence for robust matching.
 function trackPartials(frames, params) {
   const {
@@ -134,19 +149,8 @@ function trackPartials(frames, params) {
       const predictedPhase = lastPhase + phaseAdvance;
       
       const tol = Math.max(predictedFreq * trackingRatio, minTrackingHz);
-      let bestIdx = -1, bestCost = Infinity;
-
       // Find the peak in the new frame with the lowest cost (freq + phase error).
-      for (let i = 0; i < frame.peaks.length; ++i) {
-        if (matched.has(i)) continue;
-        const pk = frame.peaks[i];
-        const freqError = Math.abs(pk.freq - predictedFreq);
-        if (freqError > tol) continue;
-
-        const phaseError = Math.abs(normalizeAngle(pk.phase - predictedPhase));
-        const cost = freqError + phaseErrorWeight * phaseError * predictedFreq;
-        if (cost < bestCost) { bestCost = cost; bestIdx = i; }
-      }
+      const { bestIdx } = findBestPeak(frame.peaks, matched, predictedFreq, predictedPhase, tol, phaseErrorWeight);
 
       if (bestIdx >= 0) {
         const pk = frame.peaks[bestIdx];
@@ -175,18 +179,7 @@ function trackPartials(frames, params) {
       const predictedPhase = lastPhase + phaseAdvance;
 
       const tol = Math.max(predictedFreq * trackingRatio, minTrackingHz);
-      let bestIdx = -1, bestCost = Infinity;
-
-      for (let j = 0; j < frame.peaks.length; ++j) {
-        if (matched.has(j)) continue;
-        const pk = frame.peaks[j];
-        const freqError = Math.abs(pk.freq - predictedFreq);
-        if (freqError > tol) continue;
-        
-        const phaseError = Math.abs(normalizeAngle(pk.phase - predictedPhase));
-        const cost = freqError + phaseErrorWeight * phaseError * predictedFreq;
-        if (cost < bestCost) { bestCost = cost; bestIdx = j; }
-      }
+      const { bestIdx } = findBestPeak(frame.peaks, matched, predictedFreq, predictedPhase, tol, phaseErrorWeight);
 
       if (bestIdx >= 0) {
         const pk = frame.peaks[bestIdx];
diff --git a/tools/mq_editor/mq_synth.js b/tools/mq_editor/mq_synth.js
index 2d4cf1b..4c68056 100644
--- a/tools/mq_editor/mq_synth.js
+++ b/tools/mq_editor/mq_synth.js
@@ -1,19 +1,6 @@
 // MQ Synthesizer
 // Replica oscillator bank for sinusoidal synthesis, plus two-pole resonator mode
 
-// Evaluate cubic bezier curve at time t
-function evalBezier(curve, t) {
-  const dt = curve.t3 - curve.t0;
-  if (dt <= 0) return curve.v0;
-  let u = (t - curve.t0) / dt;
-  u = Math.max(0, Math.min(1, u));
-  const u1 = 1.0 - u;
-  return u1*u1*u1 * curve.v0 +
-         3*u1*u1*u * curve.v1 +
-         3*u1*u*u  * curve.v2 +
-         u*u*u     * curve.v3;
-}
-
 // Deterministic LCG PRNG
 function randFloat(seed, min, max) {
   seed = (1664525 * seed + 1013904223) % 0x100000000;
diff --git a/tools/mq_editor/utils.js b/tools/mq_editor/utils.js
new file mode 100644
index 0000000..c38b1f5
--- /dev/null
+++ b/tools/mq_editor/utils.js
@@ -0,0 +1,36 @@
+// Shared utilities for mq_editor
+
+// Evaluate cubic bezier curve at time t (robust: handles dt<=0)
+function evalBezier(curve, t) {
+  const dt = curve.t3 - curve.t0;
+  if (dt <= 0) return curve.v0;
+  let u = (t - curve.t0) / dt;
+  u = Math.max(0, Math.min(1, u));
+  const u1 = 1.0 - u;
+  return u1*u1*u1 * curve.v0 +
+         3*u1*u1*u * curve.v1 +
+         3*u1*u*u  * curve.v2 +
+         u*u*u     * curve.v3;
+}
+
+// Get canvas-relative {x, y} from a mouse event
+function getCanvasCoords(e, canvas) {
+  const rect = canvas.getBoundingClientRect();
+  return { x: e.clientX - rect.left, y: e.clientY - rect.top };
+}
+
+// Build upper/lower band point arrays for a frequency curve.
+// factorAbove/factorBelow are fractional offsets (e.g. 0.02 = ±2%).
+// Returns { upper: [[x,y],...], lower: [[x,y],...] }
+function buildBandPoints(viewer, curve, factorAbove, factorBelow) {
+  const STEPS = 60;
+  const upper = [], lower = [];
+  for (let i = 0; i <= STEPS; ++i) {
+    const t = curve.t0 + (curve.t3 - curve.t0) * i / STEPS;
+    if (t < viewer.t_view_min - 0.01 || t > viewer.t_view_max + 0.01) continue;
+    const f = evalBezier(curve, t);
+    upper.push([viewer.timeToX(t), viewer.freqToY(f * (1 + factorAbove))]);
+    lower.push([viewer.timeToX(t), viewer.freqToY(f * (1 - factorBelow))]);
+  }
+  return { upper, lower };
+}
diff --git a/tools/mq_editor/viewer.js b/tools/mq_editor/viewer.js
index 76c57e2..2575cac 100644
--- a/tools/mq_editor/viewer.js
+++ b/tools/mq_editor/viewer.js
@@ -288,15 +288,7 @@ class SpectrogramViewer {
     const sa = rep.spread_above != null ? rep.spread_above : 0.02;
     const sb = rep.spread_below != null ? rep.spread_below : 0.02;
 
-    const STEPS = 60;
-    const upper = [], lower = [];
-    for (let i = 0; i <= STEPS; ++i) {
-      const t = curve.t0 + (curve.t3 - curve.t0) * i / STEPS;
-      if (t < this.t_view_min - 0.01 || t > this.t_view_max + 0.01) continue;
-      const f = evalBezier(curve, t);
-      upper.push([this.timeToX(t), this.freqToY(f * (1 + sa))]);
-      lower.push([this.timeToX(t), this.freqToY(f * (1 - sb))]);
-    }
+    const {upper, lower} = buildBandPoints(this, curve, sa, sb);
     if (upper.length < 2) return;
 
     const savedAlpha = ctx.globalAlpha;
@@ -327,14 +319,7 @@ class SpectrogramViewer {
     ctx.setLineDash([]);
 
     // 50% drop-off reference lines (dotted, dimmer)
-    const p5upper = [], p5lower = [];
-    for (let i = 0; i <= STEPS; ++i) {
-      const t = curve.t0 + (curve.t3 - curve.t0) * i / STEPS;
-      if (t < this.t_view_min - 0.01 || t > this.t_view_max + 0.01) continue;
-      const f = evalBezier(curve, t);
-      p5upper.push([this.timeToX(t), this.freqToY(f * 1.50)]);
-      p5lower.push([this.timeToX(t), this.freqToY(f * 0.50)]);
-    }
+    const {upper: p5upper, lower: p5lower} = buildBandPoints(this, curve, 0.50, 0.50);
     if (p5upper.length >= 2) {
       ctx.globalAlpha = 0.55;
       ctx.strokeStyle = color;
@@ -572,9 +557,7 @@ class SpectrogramViewer {
     const {canvas, tooltip} = this;
 
     canvas.addEventListener('mousedown', (e) => {
-      const rect = canvas.getBoundingClientRect();
-      const x = e.clientX - rect.left;
-      const y = e.clientY - rect.top;
+      const {x, y} = getCanvasCoords(e, canvas);
 
       // Check control point drag on selected partial
       if (this.selectedPartial >= 0 && this.selectedPartial < this.partials.length) {
@@ -593,9 +576,7 @@ class SpectrogramViewer {
     });
 
     canvas.addEventListener('mousemove', (e) => {
-      const rect = canvas.getBoundingClientRect();
-      const x = e.clientX - rect.left;
-      const y = e.clientY - rect.top;
+      const {x, y} = getCanvasCoords(e, canvas);
 
       if (this.dragState) {
         const t = Math.max(0, Math.min(this.t_max, this.canvasToTime(x)));
@@ -717,13 +698,3 @@ class SpectrogramViewer {
   }
 }
 
-// Bezier evaluation (shared utility)
-function evalBezier(curve, t) {
-  let u = (t - curve.t0) / (curve.t3 - curve.t0);
-  u = Math.max(0, Math.min(1, u));
-  const u1 = 1 - u;
-  return u1*u1*u1 * curve.v0 +
-         3*u1*u1*u * curve.v1 +
-         3*u1*u*u  * curve.v2 +
-         u*u*u     * curve.v3;
-}