"just fyi, Dave Smith has released a eurirack-format module of the Curtis-based "classic Prophet" filter, and i think is planning more eurorack/prophet modules." Warning, pedant alert :-) That eurorack filter has little to do with the 'classic Prophet' Curtis filter. It's the same filter used in most modern DSI synth based on the CEM3379, which is a combined VCF, VCA, mixer chip. I't a modern version of what was used in the likes of the OB Matrix 6, 6R & 1000. Not saying it won't sound good (not heard it), but it's not the classic Prophet 5 filter.