Detuning Oscillators

This tutorial shows how the slight detuning of parallel oscillators can create an insteresting chorusing effect which fattens out the sound.

View / Download source - Instrument source code

View / Download source - Composition source code

Let's have a closer look. 
import jm.audio.Instrument;
import jm.audio.io.*;
import jm.audio.synth.*;
import jm.music.data.Note;
import jm.audio.AudioObject;

/**
 * A multiple sawtooth instrument implementation
 * which has each wave detuned.
 * @author Andrew Brown, Nick Coleman and Andrew Sorensen
 */

public final class SuperSawInst extends Instrument{
    //----------------------------------------------
    // Attributes
    //----------------------------------------------
   
    /** The points to use in the construction of Envelopes */
    private EnvPoint[] pointArray = new EnvPoint[10];
    /** the same rate */
    private int sampleRate;
    /** The frequency ratio between wavefroms */
    private double detune;

    //----------------------------------------------
    // Constructor
    //----------------------------------------------
    /**
     * Basic default constructor to set an initial sample rate
     * @param sampleRate
     */
    public SuperSawInst(int sampleRate){
        this(sampleRate, 0.001);
    }
   
    /**
     * Basic default constructor to set an initial sample rate
     * @param sampleRate
     */
    public SuperSawInst(int sampleRate, double detune){   
        this.sampleRate = sampleRate;
        this.detune = detune;
        EnvPoint[] tempArray = {
            new EnvPoint((float)0.0, (float)0.0),
            new EnvPoint((float)0.02, (float)1.0),
            new EnvPoint((float)0.15, (float)0.6),
            new EnvPoint((float)0.9, (float)0.3),
            new EnvPoint((float)1.0, (float)0.0)
        };
        pointArray = tempArray;
    }

    //----------------------------------------------
    // Methods
    //----------------------------------------------
      
    /**
     * Initialisation method used to build the objects that
     * this instrument will use
     */
    public void createChain(){
        Oscillator wt1 = new Oscillator(this, Oscillator.SAWTOOTH_WAVE, this.sampleRate, 2);
        Oscillator wt2 = new Oscillator(this, Oscillator.SAWTOOTH_WAVE, this.sampleRate, 2);
        wt2.setFrqRatio((float)(1.0 + detune));
        Oscillator wt3 = new Oscillator(this, Oscillator.SAWTOOTH_WAVE, this.sampleRate, 2);
        wt3.setFrqRatio((float)(1.0 - detune * 2));
        Oscillator wt4 = new Oscillator(this, Oscillator.SAWTOOTH_WAVE, this.sampleRate, 2);
        wt4.setFrqRatio((float)(1.0 + detune * 2));
        Oscillator wt5 = new Oscillator(this, Oscillator.SAWTOOTH_WAVE, this.sampleRate, 2);
        wt5.setFrqRatio((float)(1.0 - detune));
        Oscillator wt6 = new Oscillator(this, Oscillator.SAWTOOTH_WAVE, this.sampleRate, 2);
        wt6.setFrqRatio((float)(1.0 + detune * 3));
        Oscillator wt7 = new Oscillator(this, Oscillator.SAWTOOTH_WAVE, this.sampleRate, 2);
        wt7.setFrqRatio((float)(1.0 - detune * 3));
        AudioObject[] waves = {wt1, wt2, wt3, wt4, wt5, wt6, wt7};
        Add add = new Add(waves);
        Envelope env = new Envelope(add, pointArray);
        Volume vol = new Volume(env);
        StereoPan span = new StereoPan(vol);
        SampleOut sout = new SampleOut(span);
    }   
}

Instrument class overview

More commentary to come.

 

Audio objects

More commentary to come.

 

Musical Example

The code below uses multiple notes played by sine waves to create a gong-like timbre.

import jm.JMC;
import jm.music.data.*;
import jm.audio.*;
import jm.util.*;
 
 /**
 * @author Andrew Brown
 */
 public final class SuperSawTest implements JMC{
	public static void main(String[] args){
		Score score = new Score("JMDemo - Audio test");
		Part part = new Part("wave", 0); 
		Phrase phr = new Phrase(0.0);
		int sampleRate = 44100;
		Instrument inst = new SuperSawInst(sampleRate);
		
		for (int i = 0; i < 16; i++) {
			Note note = new Note(C1 + (int)(Math.random() * 24),
					0.25, (int)(Math.random() * 100 + 20));
			phr.addNote(note);
		}
		
		part.addPhrase(phr);
		score.addPart(part);
         Write.au(score, "SuperSawTest.au", inst); 
    }
}

More commentary to come.

jMusic Tutorial Index

© 2001 Andrew Brown