MIDI Beep, and synchronizarion

[Carey Brown]

Not being satisfied with the Toolkit.getDefaultToolkit().beep() sound I played around with some MIDI code till I got a sound I was happy with. All was well and good until I tried to make it multi-threaded. My app that uses it launches a couple of threads and I play a Beep when they end. It is highly unlikely that any two threads would Beep at the same time but I thought I should take that into consideration so I introduced

synchronized(synth)

into the beep() method. This caused the beep() to no longer work. Can anyone tell me why?

import javax.sound.midi.MidiChannel;
import javax.sound.midi.MidiSystem;
import javax.sound.midi.MidiUnavailableException;
import javax.sound.midi.Synthesizer;

public class Beep
{
    private static final int	GUITAR = 24;
	private static final int	VOLUME = 127;
	private static final int	PITCH = 90;
	private static final int	DURATION_MILLIS = 70;
    private static Synthesizer	synth;

    static
    {
		try
		{
			synth = MidiSystem.getSynthesizer();
			synth.open();
		}
		catch( MidiUnavailableException e )
		{
			synth = null;
		}
    }
    
	public static void beep()
	{
		if( synth == null )
			return;
//		synchronized(synth) // doesn't make a sound with this (?)
		{
			MidiChannel		ch = synth.getChannels()[2];
			ch.programChange( GUITAR );
	        ch.noteOn( PITCH, VOLUME );
	        sleep( DURATION_MILLIS );
	        ch.noteOff( PITCH );
		}
	}
    
    private static void sleep( int millis )
    {
        try
		{
			Thread.sleep(millis);
		}
		catch( InterruptedException e )
		{
		}
    }
}

[Paul Clapham]

Does it make a difference if you synchronize on a different object? I.e.

    private static Synthesizer    synth;
    private static Object synthHelper = new Object(); // Synchonize on me instead

[Carey Brown]

YES! How insightful. Is there something I should learn from this when it comes to synchronize ?

[Carey Brown]

Could it be that the MIDI library was already using that to sync on?

[Carey Brown]

Here's the working version.

import java.awt.Toolkit;

import javax.sound.midi.MidiChannel;
import javax.sound.midi.MidiSystem;
import javax.sound.midi.MidiUnavailableException;
import javax.sound.midi.Synthesizer;

public class Beep
{
    private static final int	GUITAR = 24;
	private static final int	VOLUME = 127;
	private static final int	PITCH = 90;
	private static final int	DURATION_MILLIS = 70;
    private static Synthesizer	synth;
    private static final Object	syncObj = new Object();

    static
    {
		try
		{
			synth = MidiSystem.getSynthesizer();
			synth.open();
		}
		catch( MidiUnavailableException e )
		{
			synth = null;
		}
    }
    
	public static void beep()
	{
		if( synth == null )
		{
			Toolkit.getDefaultToolkit().beep();
			return;
		}
		
		synchronized( syncObj )
		{
			MidiChannel		ch = synth.getChannels()[2];
			ch.programChange( GUITAR );
	        ch.noteOn( PITCH, VOLUME );
	        sleep( DURATION_MILLIS );
	        ch.noteOff( PITCH );
		}
	}
    
    private static void sleep( int millis )
    {
        try
		{
			Thread.sleep(millis);
		}
		catch( InterruptedException e )
		{
		}
    }
}

[Carey Brown]

A programmable version. Pick your own instrument and settings.

import java.awt.Toolkit;

import javax.sound.midi.MidiChannel;
import javax.sound.midi.MidiSystem;
import javax.sound.midi.MidiUnavailableException;
import javax.sound.midi.Synthesizer;

public class Beep
{
	public final static int
		PIANO			= 0,
		HARPSICHORD		= 6,
		XYLOPHONE		= 13,
		CHURCH_ORGAN	= 19,
		REED_ORGAN		= 20,
		HARMONICA		= 22,
		GUITAR			= 24,
		ELECTRIC_GUITAR	= 27,
		VIOLIN			= 40,
		HARP			= 46,
		TIMPANI			= 47,
		TRUMPET			= 56,
		TROMBONE		= 57,
		OBOE			= 68,
		FLUTE			= 73,
		BANJO			= 105,
		STEEL_DRUMS		= 114;

    private static final int	INSTRUMENT	= GUITAR;
	private static final int	VOLUME		= 127;
	private static final int	PITCH		= 90;
	private static final long	DURATION	= 70L;
    private static final Object	syncObj = new Object();
    private static Synthesizer	synth;

    private int		instrument;
    private int		pitch;
    private int		volume;
    private long	duration; // millis
    
    static
    {
		try
		{
			synth = MidiSystem.getSynthesizer();
			synth.open();
		}
		catch( MidiUnavailableException e )
		{
			synth = null;
		}
    }
    
    public Beep()
    {
    	this.instrument	= INSTRUMENT;
    	this.pitch		= PITCH;
    	this.volume		= VOLUME;
    	this.duration	= DURATION;
    }
    
    public Beep( int instrument, int pitch, int volume, int duration )
    {
    	this.instrument	= instrument;
    	this.pitch		= pitch;
    	this.volume		= volume;
    	this.duration	= duration;
    }
    
	public void beep()
	{
		if( synth == null )
		{
			Toolkit.getDefaultToolkit().beep();
			return;
		}
		
		synchronized( syncObj )
		{
			MidiChannel		ch = synth.getChannels()[2];
			ch.programChange( instrument );
	        ch.noteOn( pitch, volume );
	        sleep( duration );
	        ch.noteOff( pitch );
		}
	}
    
    private static void sleep( long millis )
    {
        try
		{
			Thread.sleep(millis);
		}
		catch( InterruptedException e )
		{
		}
    }
}

[Paul Clapham]

Carey Brown wrote:Could it be that the MIDI library was already using that to sync on?

That was my (lucky) guess.

[Tim Holloway]

BEEP!
You have committed a grave offence:

        catch( InterruptedException e )
        {
        }

Silently eating Exceptions is a REALLY bad practice. Yes, I know, this is a "safe" case, but at a minimum you should print a "thread interrupted" message or something. If you just swallow Exceptions, they can become Mysteries. Really, really frustrating Mysteries.