feat(mq_editor): movable inner bezier control points + clamp() refactor

- P1/P2 in amp editor now draggable horizontally; t0<t1<t2<t3 enforced
- Add clamp() to utils.js; replace all Math.max/min clamping patterns
- Cursor hints: move for P1/P2, ns-resize for P0/P3
- Remove test_fft.html
- Docs: Delete key, style.css/utils.js in architecture, bezier editor section

handoff(Claude): inner control points done, clamp() adopted everywhere

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

8 files changed, 44 insertions, 248 deletions

diff --git a/tools/mq_editor/README.md b/tools/mq_editor/README.md
index 9435883..6f75a52 100644
--- a/tools/mq_editor/README.md
+++ b/tools/mq_editor/README.md
@@ -95,6 +95,7 @@ Committed partials are prepended to the partial list with full undo support.
 | `C` | Toggle ≋ Contour mode (iso-energy tracking) |
 | `P` | Toggle raw peak overlay |
 | `A` | Toggle mini-spectrum: original ↔ synthesized |
+| `Delete` | Delete selected partial |
 | `Esc` | Exit explore/contour mode · deselect partial |
 | `Ctrl+Z` | Undo |
 | `Ctrl+Y` / `Ctrl+Shift+Z` | Redo |
@@ -104,10 +105,12 @@ Committed partials are prepended to the partial list with full undo support.
 ## Architecture
 
 - `index.html` — UI, playback, extraction orchestration, keyboard shortcuts
+- `style.css` — All UI styles (extracted from inline styles)
 - `editor.js` — Property panel and amplitude bezier editor for selected partials
 - `fft.js` — Cooley-Tukey radix-2 FFT + STFT cache
 - `mq_extract.js` — MQ algorithm: peak detection, forward tracking, backward expansion, bezier fitting
 - `mq_synth.js` — Oscillator bank + two-pole resonator synthesis from extracted partials
+- `utils.js` — Shared helpers: `evalBezier`, `evalBezierAmp`, `clamp`, canvas coordinate utilities
 - `viewer.js` — Visualization: coordinate API, spectrogram, partials, mini-spectrum, mouse/zoom
 
 ### viewer.js coordinate API
@@ -123,6 +126,19 @@ Committed partials are prepended to the partial list with full undo support.
 | `normalizeDB(db, maxDB)` | dB → intensity [0..1] over 80 dB range |
 | `partialColor(p)` | partial index → display color |
 
+## Amplitude Bezier Editor
+
+The bottom panel shows the amplitude envelope for the selected partial as a **Lagrange interpolating curve** through four control points P0–P3.
+
+- **P0, P3** (endpoints): drag vertically to adjust amplitude at the start/end of the partial. Time positions are fixed to `t_start`/`t_end`.
+- **P1, P2** (inner points): drag in **both axes** — vertically for amplitude, horizontally for time position. The ordering constraint `t0 < t1 < t2 < t3` is enforced automatically.
+
+Cursor hints: `ns-resize` for P0/P3, `move` for P1/P2.
+
+All four time and amplitude values are also editable as numbers in the property panel above.
+
+---
+
 ## Post-Synthesis Filters
 
 Global LP/HP filters applied after the oscillator bank, before normalization.
@@ -200,7 +216,7 @@ For a partial at 440 Hz with `spread = 0.02`: `BW ≈ 8.8 Hz`, `r ≈ exp(−πÂ
   - [x] Synthesized STFT cache for FFT comparison
 - [x] Phase 3: Editing UI
   - [x] Partial selection with property panel (freq/amp/synth tabs)
-  - [x] Amplitude bezier drag editor
+  - [x] Amplitude bezier drag editor (P1/P2 horizontally movable, ordering constrained)
   - [x] Synth params with jog sliders (decay, jitter, spread)
   - [x] Auto-spread detection per partial and global
   - [x] Mute / delete partials
diff --git a/tools/mq_editor/app.js b/tools/mq_editor/app.js
index 9b05789..dd0a24f 100644
--- a/tools/mq_editor/app.js
+++ b/tools/mq_editor/app.js
@@ -4,13 +4,13 @@
 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);
+  return Math.acos(clamp(cosW, -1, 1)) * 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);
+  return Math.acos(clamp(cosW, -1, 1)) * sr / (2 * Math.PI);
 }
 function fmtHz(f) {
   return f >= 1000 ? (f/1000).toFixed(1) + 'k' : Math.round(f) + 'Hz';
diff --git a/tools/mq_editor/editor.js b/tools/mq_editor/editor.js
index a7d0879..6ea6d73 100644
--- a/tools/mq_editor/editor.js
+++ b/tools/mq_editor/editor.js
@@ -322,10 +322,10 @@ class PartialEditor {
       if (!dragging) return;
       const dx = e.clientX - startX;
       const half = slider.offsetWidth / 2;
-      const clamped = Math.max(-half, Math.min(half, dx));
+      const clamped = clamp(dx, -half, half);
       thumb.style.transition = 'none';
       thumb.style.left = `calc(50% - 3px + ${clamped}px)`;
-      const newVal = Math.max(min, Math.min(max, startVal + dx * sensitivity));
+      const newVal = clamp(startVal + dx * sensitivity, min, max);
       inp.value = newVal.toFixed(decimals);
       onUpdate(newVal);
     };
@@ -496,7 +496,7 @@ class PartialEditor {
         if (Math.hypot(this._tToX(curve['t' + i]) - x, this._ampToY(curve['a' + i]) - y) <= 8) {
           if (this.onBeforeChange) this.onBeforeChange();
           this._dragPointIndex = i;
-          canvas.style.cursor  = 'grabbing';
+          canvas.style.cursor  = (i === 1 || i === 2) ? 'move' : 'ns-resize';
           e.preventDefault();
           return;
         }
@@ -510,6 +510,12 @@ class PartialEditor {
         const curve = this.partials[this._selectedIndex].freqCurve;
         const i     = this._dragPointIndex;
         curve['a' + i] = Math.max(0, this._yToAmp(y));
+        // Inner control points are also horizontally draggable
+        if (i === 1) {
+          curve.t1 = clamp(this._xToT(x), curve.t0 + 1e-4, curve.t2 - 1e-4);
+        } else if (i === 2) {
+          curve.t2 = clamp(this._xToT(x), curve.t1 + 1e-4, curve.t3 - 1e-4);
+        }
         this._renderAmpEditor();
         if (this.viewer) this.viewer.render();
         e.preventDefault();
@@ -520,13 +526,14 @@ class PartialEditor {
       if (this._selectedIndex >= 0 && this.partials) {
         const curve = this.partials[this._selectedIndex]?.freqCurve;
         if (curve) {
-          let near = false;
+          let cursor = 'crosshair';
           for (let i = 0; i < 4; ++i) {
             if (Math.hypot(this._tToX(curve['t' + i]) - x, this._ampToY(curve['a' + i]) - y) <= 8) {
-              near = true; break;
+              cursor = (i === 1 || i === 2) ? 'move' : 'ns-resize';
+              break;
             }
           }
-          canvas.style.cursor = near ? 'grab' : 'crosshair';
+          canvas.style.cursor = cursor;
         }
       }
     });
diff --git a/tools/mq_editor/mq_extract.js b/tools/mq_editor/mq_extract.js
index 18897fb..42215d3 100644
--- a/tools/mq_editor/mq_extract.js
+++ b/tools/mq_editor/mq_extract.js
@@ -451,7 +451,7 @@ function trackIsoContour(stftCache, seedTime, seedFreq, params) {
   }
 
   const seedFrame = stftCache.getFrameAtIndex(seedFrameIdx);
-  const seedBin   = Math.max(1, Math.min(halfBins - 2, Math.round(seedFreq / binHz)));
+  const seedBin   = clamp(Math.round(seedFreq / binHz), 1, halfBins - 2);
   const targetSq  = seedFrame.squaredAmplitude[seedBin];
   if (targetSq <= 0) return null;
   const targetDB  = 10 * Math.log10(targetSq);
diff --git a/tools/mq_editor/mq_synth.js b/tools/mq_editor/mq_synth.js
index 00867a9..a9f387c 100644
--- a/tools/mq_editor/mq_synth.js
+++ b/tools/mq_editor/mq_synth.js
@@ -42,8 +42,8 @@ function synthesizeMQ(partials, sampleRate, duration, integratePhase = true, opt
       // r controls pole radius (bandwidth): r→1 = narrow, r→0 = wide.
       // gainNorm = sqrt(1 - r²) normalises steady-state output power to ~A.
       const res      = partial.resonator || {};
-      const r        = options.forceRGain ? Math.min(0.9999, Math.max(0, options.globalR))
-                     : (res.r        != null ? Math.min(0.9999, Math.max(0, res.r)) : 0.995);
+      const r        = options.forceRGain ? clamp(options.globalR, 0, 0.9999)
+                     : (res.r        != null ? clamp(res.r, 0, 0.9999) : 0.995);
       const gainComp = options.forceRGain ? options.globalGain
                      : (res.gainComp != null ? res.gainComp : 1.0);
       const gainNorm = Math.sqrt(Math.max(0, 1.0 - r * r));
@@ -131,7 +131,7 @@ function synthesizeMQ(partials, sampleRate, duration, integratePhase = true, opt
   // LP: y[n] = k1*x[n] + (1-k1)*y[n-1]  — options.k1 in (0,1], omit to bypass
   // HP: y[n] = k2*(y[n-1] + x[n] - x[n-1]) — options.k2 in (0,1], omit to bypass
   if (options.k1 != null) {
-    const k1 = Math.max(0, Math.min(1, options.k1));
+    const k1 = clamp(options.k1, 0, 1);
     let y = 0.0;
     for (let i = 0; i < numSamples; ++i) {
       y = k1 * pcm[i] + (1.0 - k1) * y;
@@ -139,7 +139,7 @@ function synthesizeMQ(partials, sampleRate, duration, integratePhase = true, opt
     }
   }
   if (options.k2 != null) {
-    const k2 = Math.max(0, Math.min(1, options.k2));
+    const k2 = clamp(options.k2, 0, 1);
     let y = 0.0, xp = 0.0;
     for (let i = 0; i < numSamples; ++i) {
       const x = pcm[i];
diff --git a/tools/mq_editor/test_fft.html b/tools/mq_editor/test_fft.html
deleted file mode 100644
index b4e7f48..0000000
--- a/tools/mq_editor/test_fft.html
+++ /dev/null
@@ -1,229 +0,0 @@
-<!DOCTYPE html>
-<!--
-  test_fft.html — Isolated FFT correctness tests for fft.js
-  Open directly in a browser (no server needed).
-
-  Tests fftForward(), realFFT(), and STFTCache from fft.js.
-
-  Test summary:
-    1  DC impulse       — all-ones input → bin 0 must equal N
-    2  Single tone      — 440 Hz pure sine → peak bin matches expected frequency
-    3  STFT magnitude   — STFTCache.getMagnitudeDB() returns loud value at 440 Hz
-    4  Pair equal       — 220 + 880 Hz, both peaks found
-    5  Pair equal       — 440 + 1320 Hz, both peaks found
-    6  Pair wide        — 300 + 3000 Hz (decade separation), both peaks found
-    7  Pair extreme     — 100 + 8000 Hz (80× ratio), both peaks found
-    8  Pair unequal     — 440 Hz + 2000 Hz at 10:1 amplitude, weak peak still found
-    9  Triplet chord    — C4 (261.63) + E4 (329.63) + G4 (392) major chord
-   10  Triplet octaves  — 110 + 220 + 440 Hz octave stack
-   11  Triplet harmonic — 500 + 1500 + 4500 Hz (1:3:9 ratio)
-   12  Triplet unequal  — 440 + 880 + 1760 Hz at 1.0 / 0.5 / 0.25 (decaying harmonics)
-
-  Pass criteria:
-    - Each expected frequency bin is found within ±guard bins (guard ≈ 2 × bin_width).
-    - Bin width = SR / N = 32000 / 4096 ≈ 7.8 Hz.
-
-  All spectra are drawn as linear-magnitude plots (0..Nyquist on x-axis).
-  Colored vertical markers show expected frequency positions.
--->
-<html>
-<head>
-<meta charset="utf-8">
-<title>FFT Test</title>
-<style>
-  body { font-family: monospace; background: #111; color: #ccc; padding: 20px; }
-  h2 { color: #fff; }
-  canvas { border: 1px solid #444; display: block; margin: 10px 0; }
-  .pass { color: #4f4; }
-  .fail { color: #f44; }
-  pre { background: #222; padding: 10px; }
-</style>
-</head>
-<body>
-<h2>FFT Isolation Test</h2>
-<pre id="log"></pre>
-<canvas id="spectrum" width="800" height="200"></canvas>
-<script src="fft.js"></script>
-<script>
-const log = document.getElementById('log');
-function print(msg, cls) {
-  const span = document.createElement('span');
-  if (cls) span.className = cls;
-  span.textContent = msg + '\n';
-  log.appendChild(span);
-}
-
-// --- Test 1: Single bin impulse (DC) ---
-{
-  const N = 8;
-  const real = new Float32Array([1,1,1,1,1,1,1,1]);
-  const imag = new Float32Array(N);
-  fftForward(real, imag, N);
-  const ok = Math.abs(real[0] - 8) < 1e-4 && Math.abs(imag[0]) < 1e-4;
-  print(`Test 1 DC impulse: real[0]=${real[0].toFixed(4)}  ${ok?'PASS':'FAIL'}`, ok?'pass':'fail');
-}
-
-// --- Test 2: 440 Hz peak detection ---
-{
-  const SR = 32000;
-  const N = 2048;
-  const signal = new Float32Array(N);
-  for (let i = 0; i < N; ++i)
-    signal[i] = Math.sin(2 * Math.PI * 440 * i / SR);
-
-  const spectrum = realFFT(signal);
-
-  let peakBin = 0, peakVal = 0;
-  for (let i = 0; i < N / 2; ++i) {
-    const re = spectrum[i * 2], im = spectrum[i * 2 + 1];
-    const mag = re * re + im * im;
-    if (mag > peakVal) { peakVal = mag; peakBin = i; }
-  }
-  const peakFreq = peakBin * SR / N;
-  const ok = Math.abs(peakFreq - 440) < SR / N;
-  print(`Test 2 440Hz peak: bin=${peakBin} freq=${peakFreq.toFixed(1)}Hz  ${ok?'PASS':'FAIL'}`, ok?'pass':'fail');
-
-  // Draw spectrum
-  const canvas = document.getElementById('spectrum');
-  const ctx = canvas.getContext('2d');
-  ctx.fillStyle = '#111';
-  ctx.fillRect(0, 0, canvas.width, canvas.height);
-  ctx.strokeStyle = '#0af';
-  ctx.beginPath();
-  const halfN = N / 2;
-  for (let i = 0; i < halfN; ++i) {
-    const re = spectrum[i * 2], im = spectrum[i * 2 + 1];
-    const mag = Math.sqrt(re * re + im * im) / (N / 2);
-    const x = i / halfN * canvas.width;
-    const y = canvas.height - mag * canvas.height;
-    i === 0 ? ctx.moveTo(x, y) : ctx.lineTo(x, y);
-  }
-  ctx.stroke();
-
-  // Mark 440Hz
-  ctx.strokeStyle = '#f80';
-  ctx.beginPath();
-  const x440 = peakBin / halfN * canvas.width;
-  ctx.moveTo(x440, 0); ctx.lineTo(x440, canvas.height);
-  ctx.stroke();
-  ctx.fillStyle = '#f80';
-  ctx.fillText(`440Hz (bin ${peakBin})`, x440 + 4, 16);
-}
-
-// --- Test 3: STFT getMagnitudeDB at t=0 ---
-{
-  const SR = 32000;
-  const N = 44032; // ~1.375s
-  const signal = new Float32Array(N);
-  for (let i = 0; i < N; ++i)
-    signal[i] = Math.sin(2 * Math.PI * 440 * i / SR);
-
-  const stft = new STFTCache(signal, SR, 2048, 512);
-  const db = stft.getMagnitudeDB(0.0, 440);
-  const ok = db > -10;
-  print(`Test 3 STFT getMagnitudeDB(0, 440Hz): ${db.toFixed(1)} dB  ${ok?'PASS':'FAIL'}`, ok?'pass':'fail');
-}
-
-// Helper: find top-K peaks in spectrum (bin indices), ignoring neighbors within 'guard' bins
-function findPeaks(spectrum, halfN, k, guard) {
-  const mags = new Float32Array(halfN);
-  for (let i = 0; i < halfN; ++i) {
-    const re = spectrum[i * 2], im = spectrum[i * 2 + 1];
-    mags[i] = re * re + im * im;
-  }
-  const peaks = [];
-  const used = new Uint8Array(halfN);
-  for (let p = 0; p < k; ++p) {
-    let best = -1, bestVal = 0;
-    for (let i = 1; i < halfN; ++i) {
-      if (!used[i] && mags[i] > bestVal) { bestVal = mags[i]; best = i; }
-    }
-    if (best < 0) break;
-    peaks.push(best);
-    for (let g = Math.max(0, best - guard); g <= Math.min(halfN - 1, best + guard); ++g)
-      used[g] = 1;
-  }
-  return peaks;
-}
-
-// Helper: draw labeled spectrum on a new canvas
-function drawSpectrum(label, spectrum, N, SR, markerFreqs) {
-  const halfN = N / 2;
-  const colors = ['#f80', '#0f8', '#f0f', '#08f'];
-  const canvas = document.createElement('canvas');
-  canvas.width = 800; canvas.height = 160;
-  const div = document.createElement('div');
-  div.style.cssText = 'color:#888;font-family:monospace;font-size:12px;margin-top:8px';
-  div.textContent = label;
-  document.body.appendChild(div);
-  document.body.appendChild(canvas);
-
-  const ctx = canvas.getContext('2d');
-  ctx.fillStyle = '#111';
-  ctx.fillRect(0, 0, canvas.width, canvas.height);
-  ctx.strokeStyle = '#0af';
-  ctx.beginPath();
-  for (let i = 0; i < halfN; ++i) {
-    const re = spectrum[i * 2], im = spectrum[i * 2 + 1];
-    const mag = Math.sqrt(re * re + im * im) / (N / 2);
-    const x = i / halfN * canvas.width;
-    const y = canvas.height - mag * canvas.height;
-    i === 0 ? ctx.moveTo(x, y) : ctx.lineTo(x, y);
-  }
-  ctx.stroke();
-
-  markerFreqs.forEach((f, idx) => {
-    const bin = Math.round(f * N / SR);
-    const x = bin / halfN * canvas.width;
-    ctx.strokeStyle = colors[idx % colors.length];
-    ctx.beginPath(); ctx.moveTo(x, 0); ctx.lineTo(x, canvas.height); ctx.stroke();
-    ctx.fillStyle = colors[idx % colors.length];
-    ctx.fillText(`${f}Hz`, x + 3, 14 + idx * 14);
-  });
-}
-
-// Helper: test multi-frequency signal, return pass/fail
-function testMultiFreq(label, freqs, amplitudes, SR, N, testNum) {
-  const signal = new Float32Array(N);
-  for (let i = 0; i < N; ++i)
-    for (let f = 0; f < freqs.length; ++f)
-      signal[i] += (amplitudes ? amplitudes[f] : 1.0) * Math.sin(2 * Math.PI * freqs[f] * i / SR);
-
-  const spectrum = realFFT(signal);
-  const halfN = N / 2;
-  const guard = Math.ceil(SR / N * 2); // ~2 bins tolerance
-  const peaks = findPeaks(spectrum, halfN, freqs.length, guard);
-
-  const detectedFreqs = peaks.map(b => (b * SR / N).toFixed(1));
-  const allFound = freqs.every(f => {
-    const expectedBin = Math.round(f * N / SR);
-    return peaks.some(b => Math.abs(b - expectedBin) <= guard);
-  });
-
-  const freqStr = freqs.map((f, i) => amplitudes ? `${f}Hz@${amplitudes[i].toFixed(1)}` : `${f}Hz`).join(' + ');
-  print(`Test ${testNum} ${label} [${freqStr}]: peaks=[${detectedFreqs.join(', ')}]  ${allFound?'PASS':'FAIL'}`,
-        allFound ? 'pass' : 'fail');
-
-  drawSpectrum(`Test ${testNum}: ${label} — ${freqStr}`, spectrum, N, SR, freqs);
-  return allFound;
-}
-
-const SR = 32000, N = 4096;
-
-// --- Pairs ---
-print('\n-- Pairs --');
-testMultiFreq('pair',  [220, 880],        null,            SR, N, 4);
-testMultiFreq('pair',  [440, 1320],       null,            SR, N, 5);
-testMultiFreq('pair',  [300, 3000],       null,            SR, N, 6);
-testMultiFreq('pair',  [100, 8000],       null,            SR, N, 7);
-testMultiFreq('pair unequal amp', [440, 2000], [1.0, 0.1], SR, N, 8);
-
-// --- Triplets ---
-print('\n-- Triplets --');
-testMultiFreq('triplet',         [261.63, 329.63, 392.00],          null,              SR, N, 9);  // C E G chord
-testMultiFreq('triplet',         [110, 220, 440],                   null,              SR, N, 10); // octave stack
-testMultiFreq('triplet',         [500, 1500, 4500],                 null,              SR, N, 11); // harmonic series
-testMultiFreq('triplet unequal', [440, 880, 1760], [1.0, 0.5, 0.25],SR, N, 12);                   // decaying harmonics
-</script>
-</body>
-</html>
diff --git a/tools/mq_editor/utils.js b/tools/mq_editor/utils.js
index 2c6b2f5..ed34b8e 100644
--- a/tools/mq_editor/utils.js
+++ b/tools/mq_editor/utils.js
@@ -8,7 +8,7 @@ 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));
+  u = clamp(u, 0, 1);
   const u1 = (curve.t1 - curve.t0) / dt;
   const u2 = (curve.t2 - curve.t0) / dt;
   const d0 = (-u1) * (-u2) * (-1);
@@ -29,7 +29,7 @@ function evalBezierAmp(curve, t) {
   const dt = curve.t3 - curve.t0;
   if (dt <= 0) return curve.a0;
   let u = (t - curve.t0) / dt;
-  u = Math.max(0, Math.min(1, u));
+  u = clamp(u, 0, 1);
   const u1 = (curve.t1 - curve.t0) / dt;
   const u2 = (curve.t2 - curve.t0) / dt;
   const d0 = (-u1) * (-u2) * (-1);
@@ -45,6 +45,8 @@ function evalBezierAmp(curve, t) {
   return l0 * curve.a0 + l1 * curve.a1 + l2 * curve.a2 + l3 * curve.a3;
 }
 
+function clamp(v, lo, hi) { return v < lo ? lo : v > hi ? hi : v; }
+
 // Get canvas-relative {x, y} from a mouse event
 function getCanvasCoords(e, canvas) {
   const rect = canvas.getBoundingClientRect();
diff --git a/tools/mq_editor/viewer.js b/tools/mq_editor/viewer.js
index d7b5ac1..1bc5fc9 100644
--- a/tools/mq_editor/viewer.js
+++ b/tools/mq_editor/viewer.js
@@ -109,7 +109,7 @@ class SpectrogramViewer {
 
   // DB value -> normalized intensity [0..1], relative to cache maxDB over 80dB range
   normalizeDB(magDB, maxDB) {
-    return Math.max(0, Math.min(1, (magDB - (maxDB - 80)) / 80));
+    return clamp((magDB - (maxDB - 80)) / 80, 0, 1);
   }
 
   // Partial index -> display color
@@ -643,8 +643,8 @@ class SpectrogramViewer {
       const {x, y} = getCanvasCoords(e, canvas);
 
       if (this.dragState) {
-        const t = Math.max(0, Math.min(this.t_max, this.canvasToTime(x)));
-        const v = Math.max(this.freqStart, Math.min(this.freqEnd, this.canvasToFreq(y)));
+        const t = clamp(this.canvasToTime(x), 0, this.t_max);
+        const v = clamp(this.canvasToFreq(y), this.freqStart, this.freqEnd);
         const partial = this.partials[this.selectedPartial];
         const i = this.dragState.pointIndex;
         partial.freqCurve['t' + i] = t;