Apple

Hi,

I am just getting to grips with MusicPlayer, MusicSequence et al on iOS5 and as a first app I thought I’d write a little drum machine. I have loaded the drums into an AUSampler from a .aupreset file and then I create a MusicTrack for each drum (so that I can mute/solo each) I set the tracks kSequenceTrackProperty_LoopInfo and kSequenceTrackProperty_TrackLength appropriately. So far so good – I now have my drum loop playing nicely.

The problem comes when I start to edit the track as it plays – occasionally when I add or remove a note from the track the entire track will stop playing. After quite a bit of testing to try and find a pattern the way that I can get this to happen most regularly is to add or remove a note to start of the track just at it loops or slightly before it loops (it does not seem to occur if I do this just after the track has looped). There also seems to be a link between the length of the recorded sample and size of the zone where toggling a note on/off will cause problems – the closed hi-hat which is short has a much smaller ‘problem zone’ than the longer kick drum (in all cases however the duration of the MidiNoteMessage added to the track is the same).

When adding a new note to the track I just use a call to MusicTrackNewMIDINoteEvent. When removing a note I have tried both calling MusicTrackClear and re-adding all the notes for that track as well as iterating over the events in the track and removing the specific one at the correct time step. I also tried re-setting the loop info and track length after editing a track in case this was getting lost in the edit.

Am I doing something fundamentally wrong here? I have tried everything that I can think off to fix this problem but haven’t come up with anything that helps.

Thanks in advance,

Neil