desc: Mono

slider1:20000<20,20000,1>frequency (Hz)
slider2:0<-24,24,1>resonance (dB)

@init
mX1 = 0;
mX2 = 0;
mY1 = 0;
mY2 = 0;
pi = 22/7;

@slider
cutoff = 2 * slider1 / srate;
res = pow(10, 0.05 * - slider2);
k = 0.5 * res * sin(pi * cutoff);
c1 = 0.5 * (1 - k) / (1 + k);
c2 = (0.5 + c1) * cos(pi * cutoff);
c3 = (0.5 + c1 - c2) * 0.25;
    
mA0 = 2 * c3;
mA1 = 2 * 2 * c3;
mA2 = 2 * c3;
mB1 = 2 * -c2;
mB2 = 2 * c1;

@sample
input=0.5*(spl0+spl1);

output = mA0*input + mA1*mX1 + mA2*mX2 - mB1*mY1 - mB2*mY2;

mX2 = mX1;
mX1 = input;
mY2 = mY1;
mY1 = output;

spl0=output;
spl1=output;
