diff --git a/src/extensions/scratch3_music/index.js b/src/extensions/scratch3_music/index.js
index 6202b2ce..6d391bb9 100644
--- a/src/extensions/scratch3_music/index.js
+++ b/src/extensions/scratch3_music/index.js
@@ -60,6 +60,15 @@ class Scratch3MusicBlocks {
          */
         this._instrumentBufferArrays = [];
 
+        /**
+         * An array of audio bufferSourceNodes. Each time you play an instrument or drum sound,
+         * a bufferSourceNode is created. We keep references to them to make sure their onended
+         * events can fire.
+         * @type {Array}
+         * @private
+         */
+        this._bufferSources = [];
+
         this._loadAllSounds();
     }
 
@@ -555,9 +564,14 @@ class Scratch3MusicBlocks {
         bufferSource.buffer = this._drumBuffers[drumNum];
         bufferSource.connect(outputNode);
         bufferSource.start();
+
+        const bufferSourceIndex = this._bufferSources.length;
+        this._bufferSources.push(bufferSource);
+
         this._concurrencyCounter++;
         bufferSource.onended = () => {
             this._concurrencyCounter--;
+            delete this._bufferSources[bufferSourceIndex];
         };
     }
 
@@ -638,6 +652,10 @@ class Scratch3MusicBlocks {
         // Create the audio buffer to play the note, and set its pitch
         const context = util.runtime.audioEngine.audioContext;
         const bufferSource = context.createBufferSource();
+
+        const bufferSourceIndex = this._bufferSources.length;
+        this._bufferSources.push(bufferSource);
+
         bufferSource.buffer = this._instrumentBufferArrays[inst][sampleIndex];
         const sampleNote = sampleArray[sampleIndex];
         bufferSource.playbackRate.value = this._ratioForPitchInterval(note - sampleNote);
@@ -667,6 +685,7 @@ class Scratch3MusicBlocks {
         this._concurrencyCounter++;
         bufferSource.onended = () => {
             this._concurrencyCounter--;
+            delete this._bufferSources[bufferSourceIndex];
         };
     }