Compander compressor, expander, limiter, gate, ducker

Compander.ar(in, control, thresh, slopeBelow, slopeAbove, 

clampTime, relaxTime, mul, add)

General purpose (hard-knee) dynamics processor. 

in: The signal to be compressed / expanded / gated.

control: The signal whose amplitude determines the gain applied to the input signal. Often the same as in (for standard gating or compression) but should be different for ducking.

thresh: Control signal amplitude threshold, which determines the break point between slopeBelow and slopeAbove. Usually 0..1. The control signal amplitude is calculated using RMS.

slopeBelow: Slope of the amplitude curve below the threshold. If this slope > 1.0, the amplitude will drop off more quickly the softer the control signal gets; when the control signal is close to 0 amplitude, the output should be exactly zero -- hence, noise gating. Values < 1.0 are possible, but it means that a very low-level control signal will cause the input signal to be amplified, which would raise the noise floor.

slopeAbove: Same thing, but above the threshold. Values < 1.0 achieve compression (louder signals are attenuated); > 1.0, you get expansion (louder signals are made even louder). For 3:1 compression, you would use a value of 1/3 here.

clampTime: The amount of time it takes for the amplitude adjustment to kick in fully. This is usually pretty small, not much more than 10 milliseconds (the default value). I often set it as low as 2 milliseconds (0.002).

relaxTime: The amount of time for the amplitude adjustment to be released. Usually a bit longer than clampTime; if both times are too short, you can get some (possibly unwanted) artifacts.

If any of this is confusing, see http://en.wikipedia.org/wiki/Audio_level_compression

(

// example signal to process

play({

var z;

z = Decay2.ar(

Impulse.ar(8, 0,LFSaw.kr(0.3, 0, -0.3, 0.3)), 

0.001, 0.3, Mix.ar(Pulse.ar([80,81], 0.3)))

})

)

(

// noise gate

play({

var z;

z = Decay2.ar(

Impulse.ar(8, 0,LFSaw.kr(0.3, 0, -0.3, 0.3)), 

0.001, 0.3, Mix.ar(Pulse.ar([80,81], 0.3)));

Compander.ar(z, z,

thresh: MouseX.kr(0.1, 1),

slopeBelow: 10,

slopeAbove: 1,

clampTime: 0.01,

relaxTime: 0.01

);

})

)

(

// compressor

play({

var z;

z = Decay2.ar(

Impulse.ar(8, 0,LFSaw.kr(0.3, 0, -0.3, 0.3)), 

0.001, 0.3, Mix.ar(Pulse.ar([80,81], 0.3)));

Compander.ar(z, z,

thresh: MouseX.kr(0.1, 1),

slopeBelow: 1,

slopeAbove: 0.5,

clampTime: 0.01,

relaxTime: 0.01

);

})

)

(

// limiter

play({

var z;

z = Decay2.ar(

Impulse.ar(8, 0,LFSaw.kr(0.3, 0, -0.3, 0.3)), 

0.001, 0.3, Mix.ar(Pulse.ar([80,81], 0.3)));

Compander.ar(z, z,

thresh: MouseX.kr(0.1, 1),

slopeBelow: 1,

slopeAbove: 0.1,

clampTime: 0.01,

relaxTime: 0.01

);

})

)

(

// sustainer

play({

var z;

z = Decay2.ar(

Impulse.ar(8, 0,LFSaw.kr(0.3, 0, -0.3, 0.3)), 

0.001, 0.3, Mix.ar(Pulse.ar([80,81], 0.3)));

Compander.ar(z, z,

thresh: MouseX.kr(0.1, 1),

slopeBelow: 0.1,

slopeAbove: 1,

clampTime: 0.01,

relaxTime: 0.01

)*0.1;

})

)