**FOS first order filter section**

**FOS.ar(in, a0, a1, b1, mul, add)**

A standard first order filter section. Filter coefficients are given directly rather than calculated for you.

Formula is equivalent to:

out(i) = (a0 * in(i)) + (a1 * in(i-1)) + (b1 * out(i-1))

Examples:

(

// same as OnePole

{ var x;

x = LFTri.ar(0.4, 0, 0.99);

FOS.ar(LFSaw.ar(200, 0, 0.2), 1 - x.abs, 0.0, x)

}.play;

)

(

// same as OneZero

{ var x;

x = LFTri.ar(0.4, 0, 0.99);

FOS.ar(LFSaw.ar(200, 0, 0.2), 1 - x.abs, x, 0.0)

}.play;

)

(

// same as OnePole, kr

{ var x, ctl;

x = LFTri.kr(0.2, 0, 0.99);

ctl = FOS.kr(LFSaw.kr(8, 0, 0.2), 1 - x.abs, 0.0, x);

LFTri.ar(ctl * 200 + 500);

}.play;

)

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