BPF 2nd order Butterworth bandpass filter

BPF.ar(in, freq, rq, mul, add)

A second order low pass filter. 

in - input signal to be processed

freq - cutoff frequency in Hertz.

rq - the reciprocal of Q.  bandwidth / cutoffFreq. 

{ BPF.ar(Saw.ar(200,0.5), FSinOsc.kr(XLine.kr(0.7,300,20),0,3600,4000), 0.3) }.play;

{ BPF.ar(Saw.ar(200,0.5), MouseX.kr(100, 10000, 1), 0.3) }.play;

// BPF on control signals:

(

{ var vib = BPF.kr(PinkNoise.kr, MouseX.kr(1, 100, 1), 0.3) * 10;

SinOsc.ar(vib * 200 + 600) * 0.2 }.play;

)