java - 你如何在java中使用一个音序器实现多个节奏

Question

我一直在使用 Java 开发节拍器音乐应用程序，但偶然发现了一个复杂问题。考虑以下摘自的代码:https://community.oracle.com/thread/2135272 .这里的实现类似于我为获得多个节奏所做的。我遇到的唯一问题是它让事情变得有点困惑，我希望也许有人可以提供一种替代方法来最好通过使用一个音序器来获得多个速度。

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(); }
     }
}

Answer 1

documentation说:

A sequence can contain events that encapsulate standard MIDI tempo-change messages. When the sequencer processes such an event, it changes the speed of playback to reflect the indicated tempo.