The Grass Stimulators are literally just pulse generators, but it's a nice and dirty pulse (when compared to say, Tektronix or HP) and so long as I avoid the upper voltage ranges (it'll output 150 volts if I ask it to) they mate well with audio. If anyone has a tubed Grass I'm happy to answer questions (as I've glossed over a couple more potentially dangerous aspects regarding front panel stuff). My kid likes go in the studio and play rocket ship, so I've gotten in the habit of checking controls before power up.
Regarding VCO, the oscillators will soft sync to a source strong enough (in voltage), so it's possible, but a very convoluted maze to get there. I have a couple tubed VCOs made by Dymec (subset of HP) but they have mechanical chopper/vibratorss on the tubed operational amplifiers and make too much racket for me to use them.
The Grass collecting started with interest in the polygraph preamplifiers as a source of CV from body electrodes, but I never pursued the idea - they distort nicely though, so they can stay.. some day I'll play around with it. So far the RMA returns have worked well with the honour system, hahaha. I've had two returns to date - one for repair/further refinement on a custom build and another was a trade up for a wider feature set. So, no polygraph! (buy with impunity!
hahaha)
Is that a memory bank from an old computer? Or a delay line? I feel like I've seen it somewhere on line, but no, nothing that crazy is underfoot. I kind of stopped buying the big old stuff once transit costs skyrocketed. Winning a ten dollar auction no longer feels like a victory when shipping is over a hundred dollars.
May I ask what you've got planned for the Grass Instruments equipment if not for use in neurophysiology? Spend a lot of years working in that field. Have you managed to adapt the neurostimulators for audio use as tube based VCOs? Or is a polygraph test a prerequisite for all RMA product returns? 
Cheers mate!
haha
Got it last week, mainly cause bass>pedals>audio interface sounds kinda shite. It overdrives quite nicely, so it's also good for adding character to synths, summing drum loops through, etc.
