Wow, this is really great news, I have to get on with soldering LPC17 :)
Unfortunately I have no experience with modular synthesizers, so it is hard for me to refer your question about controll surface. The only thing that immediately comes to mind, is that full-controll surface may have modulation matrix similar to midibox SID. In the display mode led bars of the matrix may show output CV values (not shure if it will be usefull, but will look impressive ;))
Thinking about an external filter, I was planing a very simple interface (You called it a simple solution). Additionally, I thought about adding 'tap tempo' and 'manual envelope trigger' buttons, but I did not know how to implement it. Also envelope follower would be nice feature, but it requires additional hardware rather then software.
Now i think I will build full MB CV V2, because it is future-proof solution. It will be possible to create simple synthesizer by adding only VCO + VCF !
Other features that I think may be useful:
- Option to use 8 stage envelopes in Casio CZ style (possibly a lot of work)
- Possibility of using a note/ CV value table instead of output curve
- some SEQ V4 features (eg Note / LFO FX)
- glide option
- using all 8 CV outputs to controll polyphonic synth
Best Regards,
Przemek