This is a Korg Delta, a semi-obscure late seventies string synth/polysynth from Japan Inc. It's a fully polyphonic divide-down string synth with a separate (and combinable) basic synthesizer section. The poly synth section is unique in that it shares the divide-down architecture, so it's full poly, but it's "paraphonic", which means all the keys share one filter+filter envelope and one volume envelope. Which is fine for sustainting organ-type sounds, but no so good when trying to play percussive sounds. I actually enjoy the paraphonic envelopes in a strange way- you can set up a quick, percussive envelope, hold a chord with your right hand, and go nuts with one finger on your left hand a creating all manner of weird chordal rhythms. Without explaining all the possibilities, the paraphonic thing wouldn't be ideal for all styles, but it's fun for some stuff, and I doubt anyone would have this synth as their main instrument these days, so like, game on. The oscillator section is unique in that it's a single oscillator that only makes square waves, with four mixable sliders correlating to four different footage settings. The octave mixing ability lets you pretty accurately fake saw waves and all kinds of subtle variations, so "square-wave only" isn't as much of a limitation as it might seem. Finally, there's a sweet, honky-sounding old-school Korg filter with lowpass and bandpass modes- it's a really unique sounding filter (though I'm not convinced that the horizontally-oriented cutoff slider offers any benefit over a vertical one). I bought my first Delta a couple months back for $300, but it was pretty beat up. I liked it so much I decided that 1) I wanted a nicer one, and 2) I wanted to MIDI it. Now, the finding another one took me a couple of months, but I recently snared a mint one off the Vintage Synth Explorer classifieds for $600 (still awaiting delivery). MIDI, unfortunately is going to be a whole other can of worms. Remember the divide-down voicing architecture I mentioned? Here's a basic rundown of how it works- a single master oscillator runs at a REALLY high frequency and a special divider chip divides its frequency into the twelve notes of the scale. Then three more chips divide those frequencies into all the octaves needed. Unlike most polysynths, that use a matrixing system to greatly reduce the number of physical connections from the keyboard, each key of the Delta's keyboard is individually wired to the octave divider chips. What all this means is that only way to MIDI a Delta is to wire in a MIDI converter that's essentially turning each of the keyboard's 49 keys on and off. Ick. How to do this? Well after much searching the interwebs, I found that German synth maker Doepfer makes the MTC64 pre-assembled board that converts incoming MIDI to 64 pins, each outputting 5 volts corresponding to consecutive MIDI note on-off events. After futzing around inside the Delta with a multimeter, I figured out that each key carries 15 volts, and when pressed, goes to about 1 volt, thus triggering a note. Now all I have to do is figure out how to turn the MTC64's +5v into a way to drop +15v to +1 volt for each key. I'm guessing this entails a whole bunch of transistors and resistors... I'm sure it can be done. I just need to poke around some more, then build an auxilary board for this... x 49 keys! Yikes. Stay tuned.