Korg MS-10 Theremin????

I wouldn't recommend using the dictaphone for echo.

Years ago I was given this "ancient" answering machine that was as big as a microwave oven. I managed to hook it up to use as a tape echo but quickly realized that I could do much better from scratch. Answering machines typically only have a range of about 300Hz - 2kHz and very limited dynamic range.

Using the old reel-to-reel would be an interesting project, but you would want to find a few more playback heads to space around the tape path ("variable taps") and each would need its own preamp with NAB equalization.

Don

[i]"Now my plan is to take an old suitcase tube reel to reel machine ... "[/i]

If your old valve R-R is working (or can be repaired) think hard about it before you dismembr it! You may find it is more valuable than you think! - Even if its not 'valuable', these can be used as mastering tools - Used for processing a track to give it a sonic quality unmatched (in my opinion) by any of the DSP processors one can buy..

Record your mster onto it, play it back and record the playback (either directly or miked) onto a more modern format, and you can capture much of what made many '60s and earlier recordings sound, well, dated! - jokes aside though - I love some of the effects you can get from an old tape machine.. I have a few recordings I made using signal generators and LDRs, which I recorded onto an old Grundig Valve RR recorder in the late 60's.. This was then transferred to (ugh!) cassette, but it remains one of my favorite compositions and has rich musical distortion which only tape and valves can produce.
I now use a WEM Copycat - these can be picked up quite cheaply, and ar great

[i]"It will be like the spawn of an EMS Synthi A and an Ondes Martenot that mutated and sprouted antennas"[/i]

There is no comparison between a Synthi A and a Korg MS10 (except that both are HORRIBLY designed and built!) - At least the Synthi has linear CV's..

Let me tell it like it is.. from my expierience, there is little point in wasting time trying to make something from a badly designed / engineered product - The Korg will ALWAYS be an absolute PIG to interface with anything else. Even with an exponential converter, getting it to track sounds from a Theremin (like the EW) so that the Theremin and synth are in tune with each other, is not going to be easy..

I appreciate your interest in my modules - If you are waiting for these, you may as well wait a little longer - I started by developing the TherAsynth, which had a full analogue synthesiser - Once I have the core Theremin products released, I will revive the synth section as an add-on module.. In fact, I know a lot more about synths than I did about Theremins (I had designed and built an analogue 8 voice Poly synth in 1975, before Moog released theirs).

If you cannot wait, there are simple synths on-line which will give better results, and probably cost you less than adapting your Korg.

The R to R I would dismember is pretty beat-up and would need serious servicing to do anything with tape, and may have a burnt-out motor, but the amp works without too much hum.
I have another portable tube reel machine, though, that is a like new Columbia (mfg by Sony I think) and it sounds amazing--I use it as you suggest, actually. I especially like to record vocals onto it and then mic the speaker with a Telefunken D11C with everything inside a blanket-lined box and track it into the computer. Tape saturation hitting tubes and then a well-built mic is definitely some of the best compression you can get.
Concerning dictaphones, I found a broken Telefunken machine (60s era) that records onto magnetic discs on Ebay a while back. I never could get the recorder to work, but the microphone is the perfect thing for recording those narrow-band space-helmet vocals.