Multiple MIDI Sequencers In Java Applet?

Question

Hi all,
I'm working on a music applet and need to have multiple MIDI sequencers playing simultaneously. I have some test code and it works in my IDE (I'm using JGrasp) but when I try to open the applet in a web browser, it doesn't play the sequencers at the same time. It only plays one sequencer at a time and switches (seems to be random) back and forth between them instead of just letting them both play together. Is there any reason why two (or more) sequencers won't play together in an applet when they do in JGrasp? Is this just simply a limitation within applets or is there some kind of work around to fix this?
I know you can do different tracks/channels in a single sequencer, but I really need it to be separate sequencers playing simultaneously... Without getting into too much music/drum theory, I'm making a polyrhythm metronome and need to have different sequencers playing at different tempos (which you can't do with a single sequencer). If anyone has any ideas on how to get multiple sequencers to play nicely together in an applet that would be greatly appreciated.
Here is my sample program:
import java.util.*;
import javax.swing.*;
import javax.sound.midi.*;
public class MetronomeTestApplet extends JApplet
     public void init()
          MetronomeTest metTest = new MetronomeTest();
          metTest.play();
class MetronomeTest
     Sequencer sequencer1=null;
     Sequencer sequencer2=null;
     Sequence sequence1=null;
     Sequence sequence2=null;
     Track track1=null;
     Track track2=null;
     MidiEvent newEvent=null;
     int volume = 90;     
     int tempo     = 100;
     public MetronomeTest()
          try
          {     // SEQUENCER 1
               sequencer1 = MidiSystem.getSequencer();
               sequencer1.open();
               sequence1 = new Sequence(Sequence.PPQ, 16);
               track1 = sequence1.createTrack();
               ShortMessage instrumentMsg = new ShortMessage();
               instrumentMsg.setMessage(ShortMessage.PROGRAM_CHANGE, 0, 115, 0);          // 115 == woodblock
               track1.add(new MidiEvent(instrumentMsg, 0));
               // SEQUENCER 2
               sequencer2 = MidiSystem.getSequencer();
               sequencer2.open();
               sequence2 = new Sequence(Sequence.PPQ, 16);
               track2 = sequence2.createTrack();
               instrumentMsg = new ShortMessage();
               instrumentMsg.setMessage(ShortMessage.PROGRAM_CHANGE, 0, 117, 0);          // 117 == melodic tom
               track2.add(new MidiEvent(instrumentMsg, 0));
          catch (Exception e) { e.printStackTrace(); }
     public void destroy()
          sequencer1.stop();
          sequencer1.close();
          sequencer2.stop();
          sequencer2.close();
     public void play()
          try
               // LOAD SEQUENCE 1               
               for (int i=0; i<4; i++)
                    ShortMessage noteOnMsg = new ShortMessage();
                    noteOnMsg.setMessage(ShortMessage.NOTE_ON, 0, 60, volume);
                    track1.add(new MidiEvent(noteOnMsg, 0 + 16*i));
                    ShortMessage noteOffMsg = new ShortMessage();
                    noteOffMsg.setMessage(ShortMessage.NOTE_OFF, 0, 60, volume);
                    track1.add(new MidiEvent(noteOffMsg, 16 + 16*i));
               // LOAD SEQUENCE 2               
               for (int i=0; i<8; i++)
                    ShortMessage noteOnMsg = new ShortMessage();
                    noteOnMsg.setMessage(ShortMessage.NOTE_ON, 0, 60, volume);
                    track2.add(new MidiEvent(noteOnMsg, 0 + 8*i));
                    ShortMessage noteOffMsg = new ShortMessage();
                    noteOffMsg.setMessage(ShortMessage.NOTE_OFF, 0, 60, volume);
                    track2.add(new MidiEvent(noteOffMsg, 8 + 8*i));
               // LOAD AND START SEQUENCERS
               sequencer1.setSequence(sequence1);
               sequencer1.setTempoInBPM(tempo);
               sequencer1.setLoopCount(Sequencer.LOOP_CONTINUOUSLY);
               sequencer2.setSequence(sequence2);
               sequencer2.setTempoInBPM(tempo);
               sequencer2.setLoopCount(Sequencer.LOOP_CONTINUOUSLY);
               sequencer1.start();
               sequencer2.start();
          catch (Exception e) { e.printStackTrace(); }
}And the code for my html document:
<html>
<body>
<CENTER><applet code="MetronomeTestApplet.class" width="1000" height="700"></applet></CENTER>
</body>
</html>Thanks,
-tkr
Edited by: Tekker on Nov 21, 2010 5:45 PM

Answer 1

I just tried implementing the sequencers in their own threads but unfortunately it gives exactly the same results, where it works in JGrasp but not in the web browser.
Here's the threaded version:
import java.util.*;
import javax.swing.*;
import javax.sound.midi.*;
public class MetronomeTestApplet extends JApplet
     MetronomeTest metronome1;
     MetronomeTest metronome2;
     public void init()
          metronome1 = new MetronomeTest(50, 115);          // (tempo, instrument)          115 = woodblock
          metronome2 = new MetronomeTest(100, 117);          // (tempo, instrument)          117 = melodic tom     
          metronome1.start();
          metronome2.start();
     public void destroy()
          metronome1.close();
          metronome2.close();
class MetronomeTest extends Thread
     Sequencer sequencer=null;
     Sequence sequence=null;
     Track track=null;
     MidiEvent newEvent=null;
     int volume = 90;     
     int tempo = 100;
     public MetronomeTest(int tempo, int instrument)
          this.tempo = tempo;
          try
          {     sequencer = MidiSystem.getSequencer();
               sequencer.open();
               sequence = new Sequence(Sequence.PPQ, 16);
               track = sequence.createTrack();
               ShortMessage instrumentMsg = new ShortMessage();
               instrumentMsg.setMessage(ShortMessage.PROGRAM_CHANGE, 0, instrument, 0);
               track.add(new MidiEvent(instrumentMsg, 0));
          catch (Exception e) { e.printStackTrace(); }
     public void close()
          sequencer.stop();
          sequencer.close();
     public void run()
          try
          {     for (int i=0; i<4; i++)
               {     ShortMessage noteOnMsg = new ShortMessage();
                    noteOnMsg.setMessage(ShortMessage.NOTE_ON, 0, 60, volume);
                    track.add(new MidiEvent(noteOnMsg, 0 + 16*i));
                    ShortMessage noteOffMsg = new ShortMessage();
                    noteOffMsg.setMessage(ShortMessage.NOTE_OFF, 0, 60, volume);
                    track.add(new MidiEvent(noteOffMsg, 16 + 16*i));
               sequencer.setSequence(sequence);
               sequencer.setTempoInBPM(tempo);
               sequencer.setLoopCount(Sequencer.LOOP_CONTINUOUSLY);
               sequencer.start();
          catch (Exception e) { e.printStackTrace(); }
}If you have more things I can try, I'd greatly appreciate it. :)
Thanks,
-tkr