audio filters & such

I am quite interested in a device like the M Resonator

This machine is essentially a couple of filters in a feedback network. Notwithstanding any particular sound qualities their filters might have,it's a reasonably effective (& old!) idea for shaping music...and it would be fairly easy to build a crappy knock-off myself, using DIY. After all, there's plenty of schematics for the building blocks available on the web.

It's missing MIDI control though. That would be a cute arduino/mididuino project. Edit: in the sense of adding MIDI control to a filter - not simulating audio-rate DSP via an Arduino.

I'm a bit of a Korg Kaoss pad enthusiast but some kind of multi-band resonant filter - with envelope control would be a real nice thing to have as a way of shaping the spectrum of music. Actually, sounds like I'm describing a modular synth now. Especially something a little like the Doepfer A 127 module