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 - **Root cause 3:** pitch/channel always integers from msg.data[] ✅
 - **Added:** _lazyInit() called from playNote when _initialized false
 - **Oscillator fallback:** 2000ms instead of 60000ms (quick preview before init)
+
+### [2026-07-27 12:05] Task: Fix Tremolo String continuous sustain after MIDI note-off
+- **Tóm tắt thay đổi:** Root cause: `stopNote()` used CC 123 (All Notes Off) which merely enters SoundFont's release envelope. Sustained instruments like Tremolo Strings (GM#44) have 2-5s release tails. Fix: replaced CC 123 with CC 120 (All Sound Off) in `stopNote()` and `stopAll()`. CC 120 sets `voice.isActive = false` immediately, bypassing the release envelope entirely, so the note stops instantly on key release.
+- **Các file ảnh hưởng:** `app/static/js/services/soundfontPlayer.js`
+- **Ghi chú/Test (nếu có):** Test với MIDI keyboard + Tremolo Strings instrument: note tắt ngay khi release key. CC 120 tác dụng lên toàn bộ channel (kill all voices) — phù hợp với keyboard preview use-case.