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Editorial Team
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Asked: 2026-06-09T17:31:20+00:00

I’m playing a MIDI sequence via MusicPlayer which I loaded from a MIDI file

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I’m playing a MIDI sequence via MusicPlayer which I loaded from a MIDI file and I want to change the sequence to another while playback.
When I try this:

 MusicPlayerSetSequence(_player, sequence);
 MusicSequenceSetAUGraph(sequence, _processingGraph);

it stops the playback. So I start it back again and set the time with

MusicPlayerSetTime(_player, currentTime);

so it plays again where the previous sequence stopped, but there is a little delay.
I’ve tried to add the time interval to currentTime, which I got by obtaining the time before stopping and after starting again. But there is still a delay.

I was wondering if there is an alternative to stopping -> changing sequence -> starting again.

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1 Answer

  1. Editorial Team

    Because 

    MusicPlayerSetSequence(_player, sequence);
MusicSequenceSetAUGraph(sequence, _processingGraph);

    will still cause the player to stop, it is still possible to hear a little break.
    So instead of updating the musicSequence, i went ahead and changed the content of the tracks instead, which won’t cause any breaks:

    MusicTrack currentTrack;
MusicTrack currentTrack2;
MusicSequenceGetIndTrack(musicSequence, 0, &currentTrack);
MusicSequenceGetIndTrack(musicSequence, 1, &currentTrack2);
MusicTrackClear(currentTrack, 0, _trackLen);
MusicTrackClear(currentTrack2, 0, _trackLen);

MusicSequence tmpSequence;
switch (number) {
    case 0:
        tmpSequence = musicSequence1;
        break;
    case 1:
        tmpSequence = musicSequence2;
        break;
    case 2:
        tmpSequence = musicSequence3;
        break;
    case 3:
        tmpSequence = musicSequence4;
        break;

    default:
        tmpSequence = musicSequence1;
        break;
}

MusicTrack tmpTrack;
MusicTrack tmpTrack2;
MusicSequenceGetIndTrack(tmpSequence, 0, &tmpTrack);
MusicSequenceGetIndTrack(tmpSequence, 1, &tmpTrack2);
MusicTimeStamp trackLen = 0;
UInt32 trackLenLenLen = sizeof(trackLen);
MusicTrackGetProperty(tmpTrack, kSequenceTrackProperty_TrackLength, &trackLen, &trackLenLenLen);
_trackLen = trackLen;
MusicTrackCopyInsert(tmpTrack, 0, _trackLen, currentTrack, 0);
MusicTrackCopyInsert(tmpTrack2, 0, _trackLen, currentTrack2, 0);

    No disconnection of nodes, no updating the graph, no stopping the player.

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