SLUGens released under the GNU GPL as extensions for SuperCollider 3, by Nick Collins http://composerprogrammer.com/index.html
General Linear Time-Invariant (LTI) filter UGen where you specify any coefficient set via a Buffer Represents the general LTI filter difference equation in the time domain:
y(n) = b0x(n) + b1x(n-1) + ... + b(Nb)x(n-Nb) + a1y(n-1) + ... + a(Na)y(n-Na)
This is not a pole/zero view, so you'd need to calculate time domain coefficients yourself if you want to work from z-plane backwards. A corollary is, stability is not guaranteed. This is part of the fun?
You need to pass in the coefficients via two buffers, of arbitrary size.
What do you want to filter?
Feedback filter coefficients, from previous outputs
Feedforward filter coefficients, from previous inputs