无法使用java.midi.sequencer播放声音

Question

I have the following code, where I create a Sequencer, give it a Sequence, give the Sequence a new Track, write MidiEvents to the Track, and then try to play the Sequence when I call sequencer.start(). What am I doing wrong?

public static void main(String args[]) {
    try {

      Sequencer sequencer = MidiSystem.getSequencer();
      sequencer.setTempoInBPM(96);
      sequencer.setTickPosition(0);

      Sequence seq = new Sequence(Sequence.PPQ, 5);

      sequencer.setSequence(seq);

      sequencer.open();

      Track mainTrack = seq.createTrack();
      sequencer.recordEnable(mainTrack, 0);
      sequencer.startRecording();

      ShortMessage msg = new ShortMessage();
      ShortMessage msg2 = new ShortMessage();
      msg.setMessage(ShortMessage.NOTE_ON, 0, 60, 100);
      msg2.setMessage(ShortMessage.NOTE_OFF, 0, 60, 100);
      mainTrack.add(new MidiEvent(msg, 0));s
      mainTrack.add(new MidiEvent(msg2, 400));

      Thread.sleep(5000);

      sequencer.stopRecording();

      sequencer.start();

      Thread.sleep(5000);

      sequencer.close();

    } catch (MidiUnavailableException | InvalidMidiDataException | 
      InterruptedException e) {
      System.err.println(e.getMessage());
    }
}

Answer 1

1. You don't need to record, because you explicitly define the sequence you want to play.
2. You should first create the sequence with the track and the events. Then add this sequence to the sequencer and start the sequencer.
3. Furthermore: To hear anything you need a synthesizer and attach it to the sequencer.

---

public static void main(String args[]) {
try {

  Sequencer sequencer = MidiSystem.getSequencer();
  sequencer.setTempoInBPM(96);
  sequencer.setTickPosition(0);

  Sequence seq = new Sequence(Sequence.PPQ, 5);

  // sequencer.setSequence(seq);

  sequencer.open();

  Track mainTrack = seq.createTrack();
  // sequencer.recordEnable(mainTrack, 0);
  // sequencer.startRecording();

  ShortMessage msg = new ShortMessage();
  ShortMessage msg2 = new ShortMessage();
  msg.setMessage(ShortMessage.NOTE_ON, 0, 60, 100);
  msg2.setMessage(ShortMessage.NOTE_OFF, 0, 60, 100);
  mainTrack.add(new MidiEvent(msg, 0));
  mainTrack.add(new MidiEvent(msg2, 4000));

  // Thread.sleep(5000);
  // sequencer.stopRecording();

  sequencer.setSequence(seq);

  Synthesizer synth = MidiSystem.getSynthesizer();
  sequencer.getTransmitter().setReceiver(synth.getReceiver());
  synth.open();

  sequencer.start();

  Thread.sleep(5000);
  sequencer.close();

} catch (MidiUnavailableException | InvalidMidiDataException | InterruptedException e) {
  System.err.println(e.getMessage());
}
}