Multiple MIDI sounds with MusicDeviceMIDIEvent - ios

Question

I am creating MIDI sounds with MusicDeviceMIDIEvent and it's perfectly fine, I use some aupreset files I've created. One for each instrument.
My code is basically the example from apple: LoadPresetDemo. All I use is:
- (void)loadPreset:(id)sender instrumentName:(const char *)instrumentName {
NSString *presetURL1 = [NSString stringWithCString:instrumentName encoding:NSUTF8StringEncoding];
NSString *path = [[NSBundle mainBundle] pathForResource:presetURL1 ofType:#"aupreset"];
NSURL *presetURL = [[NSURL alloc] initFileURLWithPath: path];
if (presetURL) {
NSLog(#"Attempting to load preset '%#'\n", [presetURL description]);
}
else {
NSLog(#"COULD NOT GET PRESET PATH!");
}
[self loadSynthFromPresetURL: presetURL];
}
To load my aupreset file, then:
- (void) noteOn:(id)sender midiNumber:(int)midiNumber {
UInt32 noteNum = midiNumber;
UInt32 onVelocity = 127;
UInt32 noteCommand = kMIDIMessage_NoteOn << 4 | 0;
OSStatus result = noErr;
require_noerr (result = MusicDeviceMIDIEvent (self.samplerUnit, noteCommand, noteNum, onVelocity, 0), logTheError);
logTheError:
if (result != noErr) NSLog (#"Unable to start playing the low note. Error code: %d '%.4s'\n", (int) result, (const char *)&result);
}
to play the note of the previously loaded aupreset, and:
- (void) noteOff:(id)sender midiNumber:(int)midiNumber
when I want it to stop.
Now I would like to play one note of each instrument simultaneously. What is the easiest way of doing this?