feat(mq_editor): Phase 1 - MQ extraction and visualization (SPECTRAL_BRUSH_2)

Implement McAulay-Quatieri sinusoidal analysis tool for audio compression.

New files:
- doc/SPECTRAL_BRUSH_2.md: Complete design doc (MQ algorithm, data format, synthesis, roadmap)
- tools/mq_editor/index.html: Web UI (file loader, params, canvas)
- tools/mq_editor/fft.js: Radix-2 Cooley-Tukey FFT (from spectral_editor)
- tools/mq_editor/mq_extract.js: MQ algorithm (peak detection, tracking, bezier fitting)
- tools/mq_editor/viewer.js: Visualization (spectrogram, partials, zoom, axes)
- tools/mq_editor/README.md: Usage and implementation status

Features:
- Load WAV → extract sinusoidal partials → fit cubic bezier curves
- Time-frequency spectrogram with hot colormap (0-16 kHz)
- Horizontal zoom (mousewheel) around mouse position
- Axis ticks with labels (time: seconds, freq: Hz/kHz)
- Mouse tooltip showing time/frequency coordinates
- Real-time adjustable MQ parameters (FFT size, hop, threshold)

Algorithm:
- STFT with Hann windows (2048 FFT, 512 hop)
- Peak detection with parabolic interpolation
- Birth/death/continuation tracking (50 Hz tolerance)
- Cubic bezier fitting (4 control points per trajectory)

Next: Phase 2 (JS synthesizer for audio preview)

handoff(Claude): MQ editor Phase 1 complete. Ready for synthesis implementation.

5 files changed, 925 insertions, 0 deletions

diff --git a/tools/mq_editor/README.md b/tools/mq_editor/README.md
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+++ b/tools/mq_editor/README.md
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+# MQ Spectral Editor
+
+McAulay-Quatieri sinusoidal analysis and synthesis tool.
+
+## Usage
+
+```bash
+open tools/mq_editor/index.html
+```
+
+1. Load WAV file
+2. Adjust MQ parameters (FFT size, hop, threshold)
+3. Click "Extract Partials"
+4. View extracted sinusoidal trajectories with bezier curve fits
+
+## Features (Phase 1)
+
+- **MQ Extraction:** FFT → peak detection → trajectory tracking → bezier fitting
+- **Visualization:** Time-frequency plot with raw trajectories and bezier overlays
+- **Real-time:** Adjustable extraction parameters
+
+## Parameters
+
+- **FFT Size:** 1024-4096 (default 2048)
+- **Hop Size:** 64-2048 samples (default 512, 75% overlap)
+- **Threshold:** -80 to -20 dB (default -60 dB)
+
+## Architecture
+
+- `index.html` - UI and integration
+- `fft.js` - Fast Fourier Transform (Cooley-Tukey radix-2)
+- `mq_extract.js` - MQ algorithm (peak detection, tracking, bezier fitting)
+- `viewer.js` - Visualization (spectrogram, partials, zoom, mouse interaction)
+
+## Implementation Status
+
+- [x] Phase 1: MQ extraction + visualization
+  - [x] Spectrogram rendering with hot colormap
+  - [x] Horizontal zoom (mousewheel)
+  - [x] Axis ticks and labels
+  - [x] Mouse tooltip (time/frequency)
+- [ ] Phase 2: JS synthesizer (preview playback)
+- [ ] Phase 3: Editing UI (drag control points, replicas)
+- [ ] Phase 4: Export (.txt + C++ code generation)
+
+## Algorithm
+
+1. **STFT:** Overlapping Hann windows, radix-2 Cooley-Tukey FFT (from spectral_editor/dct.js)
+2. **Peak Detection:** Local maxima above threshold, parabolic interpolation
+3. **Tracking:** Birth/death/continuation (50 Hz tolerance, 2-frame persistence)
+4. **Bezier Fitting:** Cubic curves (4 control points), fixed endpoints
+
+## See Also
+
+- Design doc: `doc/SPECTRAL_BRUSH_2.md`
diff --git a/tools/mq_editor/fft.js b/tools/mq_editor/fft.js
new file mode 100644
index 0000000..8610222
--- /dev/null
+++ b/tools/mq_editor/fft.js
@@ -0,0 +1,103 @@
+// Fast Fourier Transform (adapted from spectral_editor/dct.js)
+// Radix-2 Cooley-Tukey algorithm
+
+// Bit-reversal permutation (in-place)
+function bitReversePermute(real, imag, N) {
+  let temp_bits = N;
+  let num_bits = 0;
+  while (temp_bits > 1) {
+    temp_bits >>= 1;
+    num_bits++;
+  }
+
+  for (let i = 0; i < N; ++i) {
+    let j = 0;
+    let temp = i;
+    for (let b = 0; b < num_bits; ++b) {
+      j = (j << 1) | (temp & 1);
+      temp >>= 1;
+    }
+
+    if (j > i) {
+      const tmp_real = real[i];
+      const tmp_imag = imag[i];
+      real[i] = real[j];
+      imag[i] = imag[j];
+      real[j] = tmp_real;
+      imag[j] = tmp_imag;
+    }
+  }
+}
+
+// In-place radix-2 FFT
+// direction: +1 for forward, -1 for inverse
+function fftRadix2(real, imag, N, direction) {
+  const PI = Math.PI;
+
+  for (let stage_size = 2; stage_size <= N; stage_size *= 2) {
+    const half_stage = stage_size / 2;
+    const angle = direction * 2.0 * PI / stage_size;
+
+    let wr = 1.0;
+    let wi = 0.0;
+    const wr_delta = Math.cos(angle);
+    const wi_delta = Math.sin(angle);
+
+    for (let k = 0; k < half_stage; ++k) {
+      for (let group_start = k; group_start < N; group_start += stage_size) {
+        const i = group_start;
+        const j = group_start + half_stage;
+
+        const temp_real = real[j] * wr - imag[j] * wi;
+        const temp_imag = real[j] * wi + imag[j] * wr;
+
+        real[j] = real[i] - temp_real;
+        imag[j] = imag[i] - temp_imag;
+        real[i] = real[i] + temp_real;
+        imag[i] = imag[i] + temp_imag;
+      }
+
+      const wr_old = wr;
+      wr = wr_old * wr_delta - wi * wi_delta;
+      wi = wr_old * wi_delta + wi * wr_delta;
+    }
+  }
+}
+
+// Forward FFT: Time domain → Frequency domain
+function fftForward(real, imag, N) {
+  bitReversePermute(real, imag, N);
+  fftRadix2(real, imag, N, +1);
+}
+
+// Real FFT wrapper for MQ extraction
+// Input: Float32Array (time-domain signal)
+// Output: Float32Array (interleaved [re0, im0, re1, im1, ...])
+function realFFT(signal) {
+  const N = signal.length;
+
+  // Must be power of 2
+  if ((N & (N - 1)) !== 0) {
+    throw new Error('FFT size must be power of 2');
+  }
+
+  const real = new Float32Array(N);
+  const imag = new Float32Array(N);
+
+  // Copy input to real part
+  for (let i = 0; i < N; ++i) {
+    real[i] = signal[i];
+  }
+
+  // Compute FFT
+  fftForward(real, imag, N);
+
+  // Interleave output
+  const spectrum = new Float32Array(N * 2);
+  for (let i = 0; i < N; ++i) {
+    spectrum[i * 2] = real[i];
+    spectrum[i * 2 + 1] = imag[i];
+  }
+
+  return spectrum;
+}
diff --git a/tools/mq_editor/index.html b/tools/mq_editor/index.html
new file mode 100644
index 0000000..d44f19b
--- /dev/null
+++ b/tools/mq_editor/index.html
@@ -0,0 +1,175 @@
+<!DOCTYPE html>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>MQ Spectral Editor</title>
+  <style>
+    body {
+      font-family: monospace;
+      margin: 20px;
+      background: #1a1a1a;
+      color: #ddd;
+    }
+    .toolbar {
+      margin-bottom: 10px;
+      padding: 10px;
+      background: #2a2a2a;
+      border-radius: 4px;
+    }
+    button {
+      background: #3a3a3a;
+      color: #ddd;
+      border: 1px solid #555;
+      padding: 8px 16px;
+      margin-right: 8px;
+      cursor: pointer;
+      border-radius: 4px;
+    }
+    button:hover { background: #4a4a4a; }
+    button:disabled { opacity: 0.5; cursor: not-allowed; }
+    input[type="file"] { margin-right: 16px; }
+    .params {
+      display: inline-block;
+      margin-left: 20px;
+    }
+    label {
+      margin-right: 8px;
+    }
+    input[type="number"], select {
+      width: 80px;
+      background: #3a3a3a;
+      color: #ddd;
+      border: 1px solid #555;
+      padding: 4px;
+      border-radius: 3px;
+    }
+    #canvas {
+      border: 1px solid #555;
+      background: #000;
+      cursor: crosshair;
+      display: block;
+      margin-top: 10px;
+    }
+    #status {
+      margin-top: 10px;
+      padding: 8px;
+      background: #2a2a2a;
+      border-radius: 4px;
+      min-height: 20px;
+    }
+    .info {
+      color: #4af;
+    }
+    .warn {
+      color: #fa4;
+    }
+    .error {
+      color: #f44;
+    }
+  </style>
+</head>
+<body>
+  <h2>MQ Spectral Editor</h2>
+
+  <div class="toolbar">
+    <input type="file" id="wavFile" accept=".wav">
+    <button id="extractBtn" disabled>Extract Partials</button>
+
+    <div class="params">
+      <label>FFT Size:</label>
+      <select id="fftSize">
+        <option value="1024">1024</option>
+        <option value="2048" selected>2048</option>
+        <option value="4096">4096</option>
+      </select>
+
+      <label>Hop:</label>
+      <input type="number" id="hopSize" value="512" min="64" max="2048" step="64">
+
+      <label>Threshold (dB):</label>
+      <input type="number" id="threshold" value="-60" min="-80" max="-20" step="5">
+    </div>
+  </div>
+
+  <canvas id="canvas" width="1400" height="600"></canvas>
+
+  <div id="tooltip" style="position: fixed; display: none; background: #2a2a2a; padding: 4px 8px; border: 1px solid #555; border-radius: 3px; pointer-events: none; font-size: 11px; z-index: 1000;"></div>
+
+  <div id="status">Load a WAV file to begin...</div>
+
+  <script src="fft.js"></script>
+  <script src="mq_extract.js"></script>
+  <script src="viewer.js"></script>
+  <script>
+    let audioBuffer = null;
+    let viewer = null;
+
+    const wavFile = document.getElementById('wavFile');
+    const extractBtn = document.getElementById('extractBtn');
+    const canvas = document.getElementById('canvas');
+    const status = document.getElementById('status');
+
+    const fftSize = document.getElementById('fftSize');
+    const hopSize = document.getElementById('hopSize');
+    const threshold = document.getElementById('threshold');
+
+    // Load WAV file
+    wavFile.addEventListener('change', async (e) => {
+      const file = e.target.files[0];
+      if (!file) return;
+
+      setStatus('Loading WAV...', 'info');
+      try {
+        const arrayBuffer = await file.arrayBuffer();
+        const audioContext = new AudioContext();
+        audioBuffer = await audioContext.decodeAudioData(arrayBuffer);
+
+        extractBtn.disabled = false;
+        setStatus(`Loaded: ${audioBuffer.duration.toFixed(2)}s, ${audioBuffer.sampleRate}Hz, ${audioBuffer.numberOfChannels}ch`, 'info');
+
+        // Create viewer
+        viewer = new SpectrogramViewer(canvas, audioBuffer);
+      } catch (err) {
+        setStatus('Error loading WAV: ' + err.message, 'error');
+        console.error(err);
+      }
+    });
+
+    // Extract partials
+    extractBtn.addEventListener('click', () => {
+      if (!audioBuffer) return;
+
+      setStatus('Extracting partials...', 'info');
+      extractBtn.disabled = true;
+
+      setTimeout(() => {
+        try {
+          const params = {
+            fftSize: parseInt(fftSize.value),
+            hopSize: parseInt(hopSize.value),
+            threshold: parseFloat(threshold.value),
+            sampleRate: audioBuffer.sampleRate
+          };
+
+          const partials = extractPartials(audioBuffer, params);
+
+          setStatus(`Extracted ${partials.length} partials`, 'info');
+
+          // Update viewer
+          viewer.setPartials(partials);
+
+        } catch (err) {
+          setStatus('Extraction error: ' + err.message, 'error');
+          console.error(err);
+        }
+        extractBtn.disabled = false;
+      }, 50);
+    });
+
+    function setStatus(msg, type = '') {
+      status.innerHTML = msg;
+      status.className = type;
+    }
+  </script>
+</body>
+</html>
diff --git a/tools/mq_editor/mq_extract.js b/tools/mq_editor/mq_extract.js
new file mode 100644
index 0000000..62b275c
--- /dev/null
+++ b/tools/mq_editor/mq_extract.js
@@ -0,0 +1,216 @@
+// MQ Extraction Algorithm
+// McAulay-Quatieri sinusoidal analysis
+
+// Extract partials from audio buffer
+function extractPartials(audioBuffer, params) {
+  const {fftSize, hopSize, threshold, sampleRate} = params;
+
+  // Get mono channel (mix to mono if stereo)
+  const signal = getMono(audioBuffer);
+  const numFrames = Math.floor((signal.length - fftSize) / hopSize);
+
+  // Analyze frames
+  const frames = [];
+  for (let i = 0; i < numFrames; ++i) {
+    const offset = i * hopSize;
+    const frame = signal.slice(offset, offset + fftSize);
+    const peaks = detectPeaks(frame, fftSize, sampleRate, threshold);
+    const time = offset / sampleRate;
+    frames.push({time, peaks});
+  }
+
+  // Track trajectories
+  const partials = trackPartials(frames, sampleRate);
+
+  // Fit bezier curves
+  for (const partial of partials) {
+    partial.freqCurve = fitBezier(partial.times, partial.freqs);
+    partial.ampCurve = fitBezier(partial.times, partial.amps);
+  }
+
+  return partials;
+}
+
+// Get mono signal
+function getMono(audioBuffer) {
+  const data = audioBuffer.getChannelData(0);
+  if (audioBuffer.numberOfChannels === 1) {
+    return data;
+  }
+
+  // Mix to mono
+  const left = audioBuffer.getChannelData(0);
+  const right = audioBuffer.getChannelData(1);
+  const mono = new Float32Array(left.length);
+  for (let i = 0; i < left.length; ++i) {
+    mono[i] = (left[i] + right[i]) * 0.5;
+  }
+  return mono;
+}
+
+// Detect peaks in FFT frame
+function detectPeaks(frame, fftSize, sampleRate, thresholdDB) {
+  // Apply Hann window
+  const windowed = new Float32Array(fftSize);
+  for (let i = 0; i < fftSize; ++i) {
+    const w = 0.5 - 0.5 * Math.cos(2 * Math.PI * i / fftSize);
+    windowed[i] = frame[i] * w;
+  }
+
+  // FFT (using built-in)
+  const spectrum = realFFT(windowed);
+
+  // Convert to magnitude dB
+  const mag = new Float32Array(fftSize / 2);
+  for (let i = 0; i < fftSize / 2; ++i) {
+    const re = spectrum[i * 2];
+    const im = spectrum[i * 2 + 1];
+    const magLin = Math.sqrt(re * re + im * im);
+    mag[i] = 20 * Math.log10(Math.max(magLin, 1e-10));
+  }
+
+  // Find local maxima above threshold
+  const peaks = [];
+  for (let i = 2; i < mag.length - 2; ++i) {
+    if (mag[i] > thresholdDB &&
+        mag[i] > mag[i-1] && mag[i] > mag[i-2] &&
+        mag[i] > mag[i+1] && mag[i] > mag[i+2]) {
+
+      // Parabolic interpolation for sub-bin accuracy
+      const alpha = mag[i-1];
+      const beta = mag[i];
+      const gamma = mag[i+1];
+      const p = 0.5 * (alpha - gamma) / (alpha - 2*beta + gamma);
+
+      const binFreq = (i + p) * sampleRate / fftSize;
+      const ampDB = beta - 0.25 * (alpha - gamma) * p;
+      const ampLin = Math.pow(10, ampDB / 20);
+
+      peaks.push({freq: binFreq, amp: ampLin});
+    }
+  }
+
+  return peaks;
+}
+
+// Track partials across frames (birth/death/continuation)
+function trackPartials(frames, sampleRate) {
+  const partials = [];
+  const activePartials = [];
+  const trackingThreshold = 50; // Hz
+
+  for (const frame of frames) {
+    const matched = new Set();
+
+    // Match peaks to existing partials
+    for (const partial of activePartials) {
+      const lastFreq = partial.freqs[partial.freqs.length - 1];
+
+      let bestPeak = null;
+      let bestDist = Infinity;
+
+      for (let i = 0; i < frame.peaks.length; ++i) {
+        if (matched.has(i)) continue;
+
+        const peak = frame.peaks[i];
+        const dist = Math.abs(peak.freq - lastFreq);
+
+        if (dist < trackingThreshold && dist < bestDist) {
+          bestPeak = peak;
+          bestDist = dist;
+          partial.matchIdx = i;
+        }
+      }
+
+      if (bestPeak) {
+        // Continuation
+        partial.times.push(frame.time);
+        partial.freqs.push(bestPeak.freq);
+        partial.amps.push(bestPeak.amp);
+        partial.age = 0;
+        matched.add(partial.matchIdx);
+      } else {
+        // No match
+        partial.age++;
+      }
+    }
+
+    // Birth new partials from unmatched peaks
+    for (let i = 0; i < frame.peaks.length; ++i) {
+      if (matched.has(i)) continue;
+
+      const peak = frame.peaks[i];
+      activePartials.push({
+        times: [frame.time],
+        freqs: [peak.freq],
+        amps: [peak.amp],
+        age: 0,
+        matchIdx: -1
+      });
+    }
+
+    // Death old partials
+    for (let i = activePartials.length - 1; i >= 0; --i) {
+      if (activePartials[i].age > 2) {
+        // Move to finished if long enough
+        if (activePartials[i].times.length >= 4) {
+          partials.push(activePartials[i]);
+        }
+        activePartials.splice(i, 1);
+      }
+    }
+  }
+
+  // Finish remaining active partials
+  for (const partial of activePartials) {
+    if (partial.times.length >= 4) {
+      partials.push(partial);
+    }
+  }
+
+  return partials;
+}
+
+// Fit cubic bezier curve to trajectory
+function fitBezier(times, values) {
+  if (times.length < 4) {
+    // Not enough points, just use linear segments
+    return {
+      t0: times[0], v0: values[0],
+      t1: times[0], v1: values[0],
+      t2: times[times.length-1], v2: values[values.length-1],
+      t3: times[times.length-1], v3: values[values.length-1]
+    };
+  }
+
+  // Fix endpoints
+  const t0 = times[0];
+  const t3 = times[times.length - 1];
+  const v0 = values[0];
+  const v3 = values[values.length - 1];
+
+  // Solve for interior control points via least squares
+  // Simplification: place at 1/3 and 2/3 positions
+  const t1 = t0 + (t3 - t0) / 3;
+  const t2 = t0 + 2 * (t3 - t0) / 3;
+
+  // Find v1, v2 by evaluating at nearest data points
+  let v1 = v0, v2 = v3;
+  let minDist1 = Infinity, minDist2 = Infinity;
+
+  for (let i = 0; i < times.length; ++i) {
+    const dist1 = Math.abs(times[i] - t1);
+    const dist2 = Math.abs(times[i] - t2);
+
+    if (dist1 < minDist1) {
+      minDist1 = dist1;
+      v1 = values[i];
+    }
+    if (dist2 < minDist2) {
+      minDist2 = dist2;
+      v2 = values[i];
+    }
+  }
+
+  return {t0, v0, t1, v1, t2, v2, t3, v3};
+}
diff --git a/tools/mq_editor/viewer.js b/tools/mq_editor/viewer.js
new file mode 100644
index 0000000..1b2f5bf
--- /dev/null
+++ b/tools/mq_editor/viewer.js
@@ -0,0 +1,376 @@
+// Spectrogram Viewer
+// Handles all visualization: spectrogram, partials, zoom, mouse interaction
+
+class SpectrogramViewer {
+  constructor(canvas, audioBuffer) {
+    this.canvas = canvas;
+    this.ctx = canvas.getContext('2d');
+    this.audioBuffer = audioBuffer;
+    this.partials = [];
+
+    // View state (time only, frequency fixed)
+    this.timeStart = 0;
+    this.timeEnd = audioBuffer.duration;
+    this.freqStart = 0;
+    this.freqEnd = 16000; // Fixed
+
+    // Tooltip
+    this.tooltip = document.getElementById('tooltip');
+
+    // Setup event handlers
+    this.setupMouseHandlers();
+
+    // Initial render
+    this.render();
+  }
+
+  setPartials(partials) {
+    this.partials = partials;
+    this.render();
+  }
+
+  reset() {
+    this.timeStart = 0;
+    this.timeEnd = this.audioBuffer.duration;
+    this.render();
+  }
+
+  render() {
+    this.renderSpectrogram();
+    this.renderPartials();
+    this.drawAxes();
+  }
+
+  // Render spectrogram background
+  renderSpectrogram() {
+    const {canvas, ctx, audioBuffer} = this;
+    const width = canvas.width;
+    const height = canvas.height;
+
+    ctx.fillStyle = '#000';
+    ctx.fillRect(0, 0, width, height);
+
+    const signal = getMono(audioBuffer);
+    const fftSize = 2048;
+    const hopSize = 512;
+    const sampleRate = audioBuffer.sampleRate;
+
+    const numFrames = Math.floor((signal.length - fftSize) / hopSize);
+
+    // Compute one FFT per ~4 pixels for wider bars
+    const pixelsPerFrame = 4;
+    const numDisplayFrames = Math.floor(width / pixelsPerFrame);
+
+    // Map view bounds to frame indices
+    const startFrameIdx = Math.floor(this.timeStart * sampleRate / hopSize);
+    const endFrameIdx = Math.floor(this.timeEnd * sampleRate / hopSize);
+    const visibleFrames = endFrameIdx - startFrameIdx;
+    const frameStep = Math.max(1, Math.floor(visibleFrames / numDisplayFrames));
+
+    for (let displayIdx = 0; displayIdx < numDisplayFrames; ++displayIdx) {
+      const frameIdx = startFrameIdx + displayIdx * frameStep;
+      if (frameIdx >= numFrames) break;
+
+      const offset = frameIdx * hopSize;
+      if (offset + fftSize > signal.length) break;
+
+      const frame = signal.slice(offset, offset + fftSize);
+
+      // Windowing
+      const windowed = new Float32Array(fftSize);
+      for (let i = 0; i < fftSize; ++i) {
+        const w = 0.5 - 0.5 * Math.cos(2 * Math.PI * i / fftSize);
+        windowed[i] = frame[i] * w;
+      }
+
+      // FFT
+      const spectrum = realFFT(windowed);
+
+      // Draw as vertical bar
+      const xStart = displayIdx * pixelsPerFrame;
+      const xEnd = Math.min(xStart + pixelsPerFrame, width);
+
+      // Draw frequency bins
+      const numBins = fftSize / 2;
+      for (let bin = 0; bin < numBins; ++bin) {
+        const freq = bin * sampleRate / fftSize;
+        if (freq < this.freqStart || freq > this.freqEnd) continue;
+
+        const re = spectrum[bin * 2];
+        const im = spectrum[bin * 2 + 1];
+        const mag = Math.sqrt(re * re + im * im);
+        const magDB = 20 * Math.log10(Math.max(mag, 1e-10));
+
+        const normalized = (magDB + 80) / 60;
+        const intensity = Math.max(0, Math.min(1, normalized));
+
+        const freqNorm = (freq - this.freqStart) / (this.freqEnd - this.freqStart);
+        const y = Math.floor(height - freqNorm * height);
+        if (y < 0 || y >= height) continue;
+
+        const color = this.getSpectrogramColor(intensity);
+        ctx.fillStyle = `rgb(${color.r},${color.g},${color.b})`;
+        ctx.fillRect(xStart, y, xEnd - xStart, 1);
+      }
+    }
+  }
+
+  // Render extracted partials
+  renderPartials() {
+    const {ctx, canvas, partials} = this;
+    const width = canvas.width;
+    const height = canvas.height;
+
+    const colors = [
+      '#f44', '#4f4', '#44f', '#ff4', '#f4f', '#4ff',
+      '#fa4', '#4fa', '#a4f', '#af4', '#f4a', '#4af'
+    ];
+
+    const timeDuration = this.timeEnd - this.timeStart;
+    const freqRange = this.freqEnd - this.freqStart;
+
+    for (let p = 0; p < partials.length; ++p) {
+      const partial = partials[p];
+      const color = colors[p % colors.length];
+
+      // Draw raw trajectory
+      ctx.strokeStyle = color + '44';
+      ctx.lineWidth = 1;
+      ctx.beginPath();
+
+      let started = false;
+      for (let i = 0; i < partial.times.length; ++i) {
+        const t = partial.times[i];
+        const f = partial.freqs[i];
+
+        if (t < this.timeStart || t > this.timeEnd) continue;
+        if (f < this.freqStart || f > this.freqEnd) continue;
+
+        const x = (t - this.timeStart) / timeDuration * width;
+        const y = height - (f - this.freqStart) / freqRange * height;
+
+        if (!started) {
+          ctx.moveTo(x, y);
+          started = true;
+        } else {
+          ctx.lineTo(x, y);
+        }
+      }
+
+      if (started) ctx.stroke();
+
+      // Draw bezier curve
+      if (partial.freqCurve) {
+        ctx.strokeStyle = color;
+        ctx.lineWidth = 2;
+        ctx.beginPath();
+
+        const curve = partial.freqCurve;
+        const numSteps = 50;
+
+        started = false;
+        for (let i = 0; i <= numSteps; ++i) {
+          const t = curve.t0 + (curve.t3 - curve.t0) * i / numSteps;
+          const freq = evalBezier(curve, t);
+
+          if (t < this.timeStart || t > this.timeEnd) continue;
+          if (freq < this.freqStart || freq > this.freqEnd) continue;
+
+          const x = (t - this.timeStart) / timeDuration * width;
+          const y = height - (freq - this.freqStart) / freqRange * height;
+
+          if (!started) {
+            ctx.moveTo(x, y);
+            started = true;
+          } else {
+            ctx.lineTo(x, y);
+          }
+        }
+
+        if (started) ctx.stroke();
+
+        // Draw control points
+        ctx.fillStyle = color;
+        this.drawControlPoint(curve.t0, curve.v0);
+        this.drawControlPoint(curve.t1, curve.v1);
+        this.drawControlPoint(curve.t2, curve.v2);
+        this.drawControlPoint(curve.t3, curve.v3);
+      }
+    }
+  }
+
+  // Draw control point
+  drawControlPoint(t, v) {
+    if (t < this.timeStart || t > this.timeEnd) return;
+    if (v < this.freqStart || v > this.freqEnd) return;
+
+    const timeDuration = this.timeEnd - this.timeStart;
+    const freqRange = this.freqEnd - this.freqStart;
+
+    const x = (t - this.timeStart) / timeDuration * this.canvas.width;
+    const y = this.canvas.height - (v - this.freqStart) / freqRange * this.canvas.height;
+
+    this.ctx.beginPath();
+    this.ctx.arc(x, y, 4, 0, 2 * Math.PI);
+    this.ctx.fill();
+
+    this.ctx.strokeStyle = '#fff';
+    this.ctx.lineWidth = 1;
+    this.ctx.stroke();
+  }
+
+  // Draw axes with ticks and labels
+  drawAxes() {
+    const {ctx, canvas} = this;
+    const width = canvas.width;
+    const height = canvas.height;
+
+    ctx.strokeStyle = '#666';
+    ctx.fillStyle = '#aaa';
+    ctx.font = '11px monospace';
+    ctx.lineWidth = 1;
+
+    const timeDuration = this.timeEnd - this.timeStart;
+    const freqRange = this.freqEnd - this.freqStart;
+
+    // Time axis
+    const timeStep = this.getAxisStep(timeDuration);
+    let t = Math.ceil(this.timeStart / timeStep) * timeStep;
+    while (t <= this.timeEnd) {
+      const x = (t - this.timeStart) / timeDuration * width;
+
+      ctx.beginPath();
+      ctx.moveTo(x, 0);
+      ctx.lineTo(x, height);
+      ctx.stroke();
+
+      ctx.fillText(t.toFixed(2) + 's', x + 2, height - 4);
+      t += timeStep;
+    }
+
+    // Frequency axis
+    const freqStep = this.getAxisStep(freqRange);
+    let f = Math.ceil(this.freqStart / freqStep) * freqStep;
+    while (f <= this.freqEnd) {
+      const y = height - (f - this.freqStart) / freqRange * height;
+
+      ctx.beginPath();
+      ctx.moveTo(0, y);
+      ctx.lineTo(width, y);
+      ctx.stroke();
+
+      const label = f >= 1000 ? (f/1000).toFixed(1) + 'k' : f.toFixed(0);
+      ctx.fillText(label + 'Hz', 2, y - 2);
+      f += freqStep;
+    }
+  }
+
+  // Setup mouse event handlers
+  setupMouseHandlers() {
+    const {canvas, tooltip} = this;
+
+    // Mouse move (tooltip)
+    canvas.addEventListener('mousemove', (e) => {
+      const rect = canvas.getBoundingClientRect();
+      const x = e.clientX - rect.left;
+      const y = e.clientY - rect.top;
+
+      const time = this.canvasToTime(x);
+      const freq = this.canvasToFreq(y);
+
+      tooltip.style.left = (e.clientX + 10) + 'px';
+      tooltip.style.top = (e.clientY + 10) + 'px';
+      tooltip.style.display = 'block';
+      tooltip.textContent = `${time.toFixed(3)}s, ${freq.toFixed(1)}Hz`;
+    });
+
+    canvas.addEventListener('mouseleave', () => {
+      tooltip.style.display = 'none';
+    });
+
+    // Mouse wheel (horizontal zoom only)
+    canvas.addEventListener('wheel', (e) => {
+      e.preventDefault();
+
+      const rect = canvas.getBoundingClientRect();
+      const x = e.clientX - rect.left;
+
+      // Get mouse position in time space
+      const mouseTime = this.canvasToTime(x);
+
+      // Zoom factor
+      const zoomFactor = e.deltaY > 0 ? 1.2 : 0.8;
+
+      // Zoom time around mouse position
+      const timeDuration = this.timeEnd - this.timeStart;
+      const newTimeDuration = timeDuration * zoomFactor;
+      const timeRatio = (mouseTime - this.timeStart) / timeDuration;
+
+      this.timeStart = mouseTime - newTimeDuration * timeRatio;
+      this.timeEnd = mouseTime + newTimeDuration * (1 - timeRatio);
+
+      // Clamp time bounds
+      if (this.timeStart < 0) {
+        this.timeEnd -= this.timeStart;
+        this.timeStart = 0;
+      }
+      if (this.timeEnd > this.audioBuffer.duration) {
+        this.timeStart -= (this.timeEnd - this.audioBuffer.duration);
+        this.timeEnd = this.audioBuffer.duration;
+      }
+
+      // Re-render
+      this.render();
+    });
+  }
+
+  // Coordinate conversion
+  canvasToTime(x) {
+    return this.timeStart + (x / this.canvas.width) * (this.timeEnd - this.timeStart);
+  }
+
+  canvasToFreq(y) {
+    return this.freqEnd - (y / this.canvas.height) * (this.freqEnd - this.freqStart);
+  }
+
+  // Utilities
+  getAxisStep(range) {
+    const steps = [0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000, 5000];
+    const targetSteps = 8;
+    const targetStep = range / targetSteps;
+
+    for (const step of steps) {
+      if (step >= targetStep) return step;
+    }
+
+    return steps[steps.length - 1];
+  }
+
+  getSpectrogramColor(intensity) {
+    if (intensity < 0.25) {
+      const t = intensity / 0.25;
+      return {r: 0, g: 0, b: Math.floor(t * 128)};
+    } else if (intensity < 0.5) {
+      const t = (intensity - 0.25) / 0.25;
+      return {r: 0, g: Math.floor(t * 128), b: 128};
+    } else if (intensity < 0.75) {
+      const t = (intensity - 0.5) / 0.25;
+      return {r: Math.floor(t * 255), g: 128 + Math.floor(t * 127), b: 128 - Math.floor(t * 128)};
+    } else {
+      const t = (intensity - 0.75) / 0.25;
+      return {r: 255, g: 255 - Math.floor(t * 128), b: 0};
+    }
+  }
+}
+
+// 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;
+}