Doepfer

> sound with a frequency demodulator, that you would tune to the same 
> range as the oscillator used for recording.
> Any thoughts on this?

It can be done.  you want to start at 30ips.  Morton Subotnick used 
to record control voltages to tape with a Buchla system.  I don't 
know off the top of my head if it was a 100 or 200 series music box.  
You'll just need to expirment at what works best with doepfer voltages

Good luck