Hi, The csound manual is very complete as far as opcodes and csound itself goes, but it can leave the non-initiate sadly baffled. For example, the description of the butterlp opcode reads "Implementation of a second-order low-pass Butterworth filter.". While I know what a low-pass filter is, I'm afraid that what a "second order Butterworth" lp filter is and how it differs from other lp filters is beyond me. Is there any extensive online resource such as a glossary where such information might be readily available? If not, what would people think of such a resource (possibly wiki-based) on csounds.com? My ignorance in such matters is something I keep coming up against, and I have a feeling that perhaps there are other users, at least less seasoned users, who might be experiencing the same thing. Cheers, S.M. -- smassy@sdf.lonestar.org