Generative Creativity - Lecture 6
Applet sound

Notes applet

The Notes applet below illustrates the MIDI approach.

A Sequence object is constructed consisting of a Track of MIDI note events.

This is then `played' using the Sequencer object.

Mouse clicks can be used to start and stop the sequencer.

Notes applet code

  import javax.swing.*;
  import javax.sound.midi.*;
  import java.awt.event.*;
  import java.awt.*;


  public class Notes extends JApplet implements MouseListener {
     Sequencer sequencer;

     int randomPitch() {
        return((int)(Math.random() * 127));
     }

     public void init() {
        addMouseListener(this);
        try {
           sequencer = MidiSystem.getSequencer();
           sequencer.open();
           Sequence sequence = new Sequence(Sequence.PPQ, 16);
           sequencer.setTempoInBPM(120);
           Track track = sequence.createTrack();
           for (int tick = 0; tick < 1000; tick++) {
              ShortMessage msg = new ShortMessage();
              msg.setMessage(ShortMessage.NOTE_ON, 1, randomPitch(), 100);

              track.add(new MidiEvent(msg, tick));   }
           sequencer.setSequence(sequence);
           sequencer.start();
        } catch(Exception ex) { ex.printStackTrace(); }
     }

     public void mousePressed(MouseEvent event) {
        if (sequencer.isRunning()) {
           getContentPane().setBackground(Color.red);
           sequencer.stop(); }
        else {
           getContentPane().setBackground(Color.green);
           sequencer.start(); }
     }

     public void mouseReleased(MouseEvent event) { }
     public void mouseClicked(MouseEvent event) { }
     public void mouseEntered(MouseEvent event) { }
     public void mouseExited(MouseEvent event) { }

  }

Notes applet in action

Summary

• create a Sequence with some Track objects.

• Add MidiEvents containing suitably constructed ShortMessages (e.g., NOTE_ON and NOTE_OFF messages) to one of the tracks.

• Set the sequence on the Sequencer and call start.

• For sound synthesis, consider using one of the public-domain packages such as JSyn from http://www.softsynth.com/jsyn.

Exercises

• Modify the Notes applet so that it plays notes more slowly.
• Modifyt the Notes applet so that it adds appropriate NOTE_OFF events to for each NOTE_ON event.
• Modify the Notes applet so that it generates notes in a specific key or blues scale.
• Having read the documentation for the Java Midi classes, modify the Notes applet so that it each mouse click changes the instrument used.
• Modify the applet so that it leaves randomly-sized pauses between each note.
• Modify the applet so that it generates notes from a specific melody.

Resources

Also see the documentation for the `Sequencer', `Sequence', `MidiSystem' `ShortMessage' and `MidiEvent' classes.