diff --git a/src/engine/audioEngine.js b/src/engine/audioEngine.js
index 0239e25..b38d97a 100644
--- a/src/engine/audioEngine.js
+++ b/src/engine/audioEngine.js
@@ -18,13 +18,8 @@ const keyboardState = { frequency: 440, gate: false };
 // Using integers avoids floating-point drift entirely.
 export const MASTER_TICK_RATE = 480; // Hz — must be high enough for fastest BPM
 let _masterClock = null;
-let _masterTicks = 0;
 const _tickListeners = new Map(); // id → callback(audioTime, ticks)
 
-export function getMasterTicks() {
-  return _masterTicks;
-}
-
 export function subscribeTick(id, callback) {
   _tickListeners.set(id, callback);
 }
@@ -35,11 +30,16 @@ export function unsubscribeTick(id) {
 
 function startMasterClock() {
   if (_masterClock) return;
-  _masterTicks = 0;
+  let _startTime = 0;
+  let _started = false;
   _masterClock = new Tone.Clock((time) => {
-    _masterTicks++;
+    if (!_started) { _startTime = time; _started = true; }
+    // Derive ticks from precise AudioContext.currentTime, not a counter.
+    // Counters fall behind when callbacks are delayed (GC, UI, tab throttle).
+    // The time parameter is always accurate regardless of callback jitter.
+    const ticks = Math.round((time - _startTime) * MASTER_TICK_RATE);
     for (const cb of _tickListeners.values()) {
-      cb(time, _masterTicks);
+      cb(time, ticks);
     }
   }, MASTER_TICK_RATE);
   _masterClock.start();