Hi everyone,
I am reading a book called "Head First Java" by Kathy Sierra and Bert Bates. One example piece of code uses a MIDI sequencer to generate a sound.
Unfortunately it doesn't work for me on Ubuntu. When I run it I only hear a kind of knock (it's supposed to be a piano note). I don't know anything about sound and MIDI devices, so I don't know how to fix the problem.

I give the code below.
After compiling it I execute the command with different arguments:
java MiniMusicCmdLine 102 30
java MiniMusicCmdLine 80 20
java MiniMusicCmdLine 40 70

They're supposed to produce notes of different pitch, but I always hear the same short knock.

I welcome any help at the beginner level.

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import javax.sound.midi.*;

public class MiniMiniMusicCmdLine {

public static void main(String[] args) {
MiniMiniMusicCmdLine mini = new MiniMiniMusicCmdLine();
if (args.length < 2) {
System.out.println("Don't forget the instrument and note args");
} else {
int instrument = Integer.parseInt(args[0]);
int note = Integer.parseInt(args[1]);
mini.play(instrument,note);
}
} // close main

public void play(int instrument, int note) {
try {
Sequencer player = MidiSystem.getSequencer();
player.open();
Sequence seq = new Sequence(Sequence.PPQ, 4);
Track track = seq.createTrack();

MidiEvent event = null;

ShortMessage first = new ShortMessage();
first.setMessage(192, 1, instrument, 0);
MidiEvent changeInstrument = new MidiEvent(first, 1);
track.add(changeInstrument);

ShortMessage a = new ShortMessage();
a.setMessage(144, 1, note, 100);
MidiEvent noteOn = new MidiEvent(a, 1);
track.add(noteOn);

ShortMessage b = new ShortMessage();
a.setMessage(128, 1, note, 100);
MidiEvent noteOff = new MidiEvent(b, 16);
track.add(noteOff);

player.setSequence(seq);
player.start();
} catch (Exception ex) {ex.printStackTrace();}
} // close play

} // close class