Could someone explain that the coefficients mean? (or link to some material that explains it)...
Well...... A digital filter is one big mathematical function, right? The coeficients are the numbers in the equation. Everything the filter does follows from those, the cutoff and the resonance follow from them but also wether or not the filter is stable (which kinda means "wether or not it works at all"). As I understand the theory what you have is very short delays and amplification factors and the coeficients are simply numbers like how much to amplify by at various stages before summing. The problem is that fimding what numbers represent the exact filter you need is quite hard and not so much fun to go do manually. If you want to go there I sugest a serious book on DSP. Beware that this stuff gets very serious very quickly. I wanted to have a good look at how ChucK implements this and actually started reading on DSP but then I saw that there is a plan to clean up how these work in a future version. This made me wait for this cleaning, I'd sugest you do the same.
Yeah, that looks like a nice book, might pick it up. I imagine a lot of future users being just as ignorant as me about filer coefficients and the like. So may I propose that a couple of simple to use analog style filters is added to chuck + a bit of explanation about using the current filters + links (if possible) to background material.
Yeah, I'd like to have that book too. I realise this post isn't much help but at least it should be somewhat clear *why* it's not so helpfull. What would be nice would be something like "how to deal with filters in ChucK without going insane over 1000 page tomes that asume you want to design a mobile phone". Maybe if the filters do get cleaned up Perry might write something on them, I can't imagine he designs a IIR filter for every musical piece he does. Kas.