diff --git a/app/static/js/services/soundfontPlayer.js b/app/static/js/services/soundfontPlayer.js
index 09a7d17..bdaf5a4 100644
--- a/app/static/js/services/soundfontPlayer.js
+++ b/app/static/js/services/soundfontPlayer.js
@@ -394,12 +394,13 @@
                 try {
                     console.log("[SonicSF] noteOn ch:", ch, "pitch:", midiPitch, "vel:", midiVel);
                     _fluidModule._fluid_synth_noteon(_synthPtr, ch, midiPitch, midiVel);
-                    _activeNotes[ch + ':' + midiPitch] = ch;
+                    _activeNotes[(channel !== undefined ? channel : 0) + ':' + midiPitch] = ch;
+                    var noteMapKey = (channel !== undefined ? channel : 0) + ':' + midiPitch;
                     if (durationMs > 0 && durationMs < 60000) {
                         scheduledNote.off = setTimeout(function () {
                             try {
                                 _fluidModule._fluid_synth_noteoff(_synthPtr, ch, midiPitch);
-                                delete _activeNotes[ch + ':' + midiPitch];
+                                delete _activeNotes[noteMapKey];
                             } catch (e) {}
                         }, durSec * 1000);
                     }