I am using billthefarmer/mididriver on android to play midi notes. I used this question here as the starting point. Now I can send a message to the internal android synthesizer to play a specific note on some channel with a given velocity and also to stop playing that note.
private void playNote(int noteNumber) {
// Construct a note ON message for the specified at maximum velocity on channel 1:
event = new byte[3];
event[0] = (byte) (0x90 | 0x00); // This is the channel I guess but why two hex?
event[1] = (byte) noteNumber; // specified note
event[2] = (byte) 127; // 0x7F = the maximum velocity (127)
// Internally this just calls write() and can be considered obsoleted:
//midiDriver.queueEvent(event);
// Send the MIDI event to the synthesizer.
midiDriver.write(event);
}
private void stopNote(int noteNumber) {
// Construct a note OFF message for the specified note at minimum velocity on channel 1:
event = new byte[3];
event[0] = (byte) (0x80 | 0x00); // again why two hex?
event[1] = (byte) noteNumber; // specified note
event[2] = (byte) 0x00; // 0x00 = the minimum velocity (0)
// Send the MIDI event to the synthesizer.
midiDriver.write(event);
}
From what I can infer, these messages are sent as bytes because the midi files and signals are also binary (perhaps?). Anyway, there are some questions I couldn't sort out.
- How do I construct a message to change the instrument on the channel?
I found this on the web. Is this the right way to implement?
private void selectInstrument(int instrument) {
// message to select the instrument on channel 1:
event = new byte[2];
event[0] = (byte)(0xC0 | 0x00); // Can't I use int 0 for channel 1?
event[1] = (byte)instrument;
// Send the MIDI event to the synthesizer.
midiDriver.write(event);
}
int instrument is General MIDI Level 1 Instrument Number.
How is the synthesizer deciding which message tells it to play/stop note and which one tells it to change instrument on a channel? Is it the length of byte array?
So far my app only plays a specific note based on the button pressed. If I wish to play a sequence of notes at a specific bpm. Say 180 bpm and one note per beat. I have to do all that with code? Or is there a way to feed some binary message to the synthesizer where it could play an array or sequence of specified notes at a specific rate (bpm). If so, how?
