diff --git a/src/viewport/SoundLibrary.ts b/src/viewport/SoundLibrary.ts
index a7d80d26..a42f982e 100644
--- a/src/viewport/SoundLibrary.ts
+++ b/src/viewport/SoundLibrary.ts
@@ -591,15 +591,16 @@ export class SoundLibrary implements AudioSink {
 
   /**
    * A bus by its name, made on its first use into `into`, or into the master; only the master is
-   * heard straight out (#325). It is not to go any more.
+   * heard straight out (#325). It is not to go any more. The context comes first: the one made now
+   * sets up the mix, whose bus this may be, and that one is to be kept (#369).
    */
   private bus(name: string, into: string | null = null): Bus {
+    const context = this.audio();
     const known = this.buses.get(name);
     if (known) {
       known.leaving = 0;
       return known;
     }
-    const context = this.audio();
     const target = name === MASTER_MIX ? null : (into ?? MASTER_MIX);
     const made: Bus = {
       input: context.createGain(),
diff --git a/tests/viewport/sound-library.test.ts b/tests/viewport/sound-library.test.ts
index 475fb5ca..55aa121e 100644
--- a/tests/viewport/sound-library.test.ts
+++ b/tests/viewport/sound-library.test.ts
@@ -2261,6 +2261,19 @@ describe('the master and the buses of the project (#325)', () => {
     expect(wires.filter((wire) => wire.endsWith('> destination'))).toEqual(['panner > destination']);
   });
 
+  it('keeps the mix where the first thing heard is a tab of a song, which names its bus before there is a context', async () => {
+    const library = new SoundLibrary(false);
+    await library.setMix(mix);
+    await library.setBuses([{ name: 'music:1', gain: 1, pan: 0, into: 'mix:b' }]);
+    expect(levels(library)).toEqual([
+      { name: 'mix', gain: 0.5, into: null },
+      { name: 'mix:a', gain: 1, into: 'mix' },
+      { name: 'mix:b', gain: 0.25, into: 'mix:a' },
+      { name: 'music:1', gain: 1, into: 'mix:b' },
+    ]);
+    expect(wires.filter((wire) => wire.endsWith('> destination'))).toEqual(['panner > destination']);
+  });
+
   it('plays a voice on the bus it is given, and a playing too', async () => {
     const library = new SoundLibrary(false);
     await library.setMix(mix);