"Here's an MTI model AO-1 Auto-Orchestra. Back in the day this was intended to be sort of an all purpose accompaniment machine. It included drum beats, plus accompaniments consisting of bass, strings and sort of organ chording. The bass, string and chord tones run from a set of bass foot pedals (similar to a Moog Taurus). The chords play automatically and are pattern synched to the drum beats. The bass notes can either be played fully "manually" with the pedals, or can be set to be sort of semi-arpeggiated, also synched to the drums. There was also a volume pedal that could be selected to control one or a few of the different sounds...
One other thing that I'm not too sure about -- you can see in the pictures below there's a line of switches at the bottom of the machine marked Drums, Chords, Bass and Strings. The last 3 of these are latching toggles that turn the respective sounds on and off. The Drums switch, though, doesn't latch and doesn't seem to do anything that I can determine. It's normally in the "out" position, which should be (according to the standard of the other 3 switches) drums off rather than drums on, but the drums are definitely on. So I don't don't know if it's broken or it's been modified or if that switch is intended to do something I'm not understanding. In any case, you can turn the drums off by pushing the "Start/Stop" button or by turning down (or pushing in) the drum volume control. If anybody is familiar with these machines and knows whether the Drums button is suppose to latch or what it's supposed to do, if you message me I'd love to post any information you might have here.
As far as the bass pedals go, the machine uses a very simple scheme. One of the pins on the keyboard connector is +5 volts, and each of the other pins represents one note. Just connect the 5 volts to whichever note you want to sound. You could wire this up to some yanked organ pedals like I had planned to do, or you could just put a line of momentary stomp box switches on a panel or who knows what else. I bought a male connector for the keyboard port -- it's not pictured here, but I still have it and I'll include it if you want it..."