Possible Interfaces
--------------------

    ecasound = new ECASound({
        bg:    'music1.wav',
        two:   'music2.wav',
        three: 'music3.wav'
    });

    ecasound._.bg
        .queue(40)
        .play(0)
        .until(173)
        .volume(0)
        .fade(100, 2)
        .fade( 20, 4, 'two.start   - 2')
        .fade(100, 4, 'two.end     - 2')
        .fade( 20, 4, 'three.start - 2')
        .fade(100, 4, 'three.end   - 2')
        .fade(  0, 4, 'bg.end      - 2')

    ecasound._.two
        .play(5.7)
        .volume(0)
        .fade(100, 2)
        .fade(  0, 2, 'bg.end      - 2')

    ecasound._.three
        .play(33.3)
        .volume(0)
        .fade(100, 2)
        .fade(  0, 2, 'bg.end      - 2')

    // --------------

    var oBG  = new Track('bg',    'music1.wav').queue(40);
    var oOne = new Track('two',   'music2.wav');
    var oTwo = new Track('three', 'music3.wav');

    oBG.play(0)
        .until(173)
        .volume(0)
        .fade(100, 2)
        .fade( 20, 4, 'two.start   - 2')
        .fade(100, 4, 'two.end     - 2')
        .fade( 20, 4, 'three.start - 2')
        .fade(100, 4, 'three.end   - 2')
        .fade(  0, 4, 'bg.end      - 2')

    oOne.play(5.7)
        .volume(0)
        .fade(100, 2)
        .fade(  0, 2, 'bg.end      - 2')

    oTwo.play(33.3)
        .volume(0)
        .fade(100, 2)
        .fade(  0, 2, 'bg.end      - 2')

    ecasound = new ECASound(oBG, oOne, oTwo);

    // --------------

    var oBG  = new Track('bg',    'music1.wav').queue(40);
    var oOne = new Track('two',   'music2.wav');
    var oTwo = new Track('three', 'music3.wav');

    new ECASound(
        oBG.play(0)
            .until(173)
            .volume(0)
            .fade(100, 2)
            .fade( 20, 4, 'two.start   - 2')
            .fade(100, 4, 'two.end     - 2')
            .fade( 20, 4, 'three.start - 2')
            .fade(100, 4, 'three.end   - 2')
            .fade(  0, 4, 'bg.end      - 2'),
        oOne.play(5.7)
            .volume(0)
            .fade(100, 2)
            .fade(0,   2, 'bg.end      - 2'),
        oTwo.play(33.3)
            .volume(0)
            .fade(100, 2)
            .fade(0,   2, 'bg.end      - 2')
    );