[sdiy] Sound synthesis with microcontrollers

[jbv]

Paul Maddox :

> another option might be to look at the smaller FPGAs,
> AS you can do things in parallel and create your own multipliers you could
> probably get a better 'width' for your multiply and probably faster too.

Yes, I know it's an option, and it's been discussed here
already...
Actually, I think I've put together (at least on paper)
a rather simple architecture : a fast uC (Scenix 75 MHz),
a multiplier (FPGA or Logic Devices) and some SRAM.
It should be able to run several algos, most of them
simple loops at 48 KHz.
The benefit of this approach is to allow some sort of
pipelining and parallel processing. All external i/o and
data distribution / collection would be handled via a
common bus by another  (slower) uC, probably with
onboard ADCs & DAC...
This thing is actually a sort of customized DSP emulation,
for which software should be much easier to write and
optimize than on a DSP, mainly because it would remain
simple...

The opposite approach could be a fast 16 bits uC with
plenty of features (ADC & DAC, RAM & Rom, UART...).
As said before the Philips XA family is attractive. But
someone also mentioned HItachi chips... Any link for
datasheets ?
As for the XA, lately Elektor (always a good source of
inspiration) has published a development board as well as
free software tools which should be enough for DIY
purposes...

IMHO it's the type of application that determines the
choice of a uC. If you want to emulate analog gear
(VCO -> VCF -> VCA) with MIDI control, then the
16 bits uC looks like the best option.

What I'm after is a simple and flexible architecture
that would allow several applications :
- Digital VCO with control over harmonics amp &
phase
- granular synthesis & reverb
- additive synthesis
- neural networks
- etc etc
In other words, the same board / module would be
used to implement various functions (and why not
a VC controlled switch between those functions)...
In that case, the other approach looks more convenient...

If I dare a personal opinion, straight emulation of analog
is probably a nice programming challenge for a DIYer,
but I'm not sure that  is the most interesting thing to be
done with Ucs...
I've always had the feeling that there's a whole hybrid
world combining VC and DSP style processing that
remains to be explored, both at sound level (harmonics,
grains...) and at higher musical structures level...
Including several such modules in a "traditional" analog
modular would certainly expand musical horizons...

jb