A very rare instrument is the MOOG MuSonics Sonic V from 1972 which was the predecessor of the Moog Sonic 6. It was a duophonic Synthesizer and included 2 oscillators, 1 lowpass filter with self resonance (4 pole), 1 LFO (square, triangle, saw) and one envelope generator (AD and AR). It includes CV Gate for control and triggering but unfortunately no arpeggiator or sequencer. Due of the retrigger of the envelope by the LFO’s, this instrument was great for self-playing patches. Check out the video below to get an idea how this synth sounds. Thanks to sequencer.de for the deeper informations about this rare instrument.
More informations here: Moog MuSonics Sonic V 1972