This is the rare Korg 900PS analog Preset Synthesizer. There seems to be some confusion about the naming (sometimes called PS900), especially since the face plate says "Synthesizer Korg Preset." The 900PS is quite a basic but very interesting monosynth. The 900PS definitely 'borrowed' some ideas from the Pro-Soloist. Instant selection of 29 different tone colors. From the sweet sound of a violin to the chugging of a steam locomotive. Sensitive soft-touch switches and plentiful controls provide a wide variety of effects including vibrato, repeat, even the harmonics you need for a Hammond organ tone.
The 900PS has 29 presets: Timpani, Electric Bass, Synthe Bass, Piano, Harpsichord, Shamisen, Banjo, Mandolin, Xylophone, Tuba, Bassoon, Horn, Cello, Trombone, Saxophone, Voice, Clarinet, Accordion, Trumpet, Funky Trumpet, Synthe Trumpet, Oboe, Violin, Recorder, White Noise, Scale Noise, Harmonics I, Harmonics II, Harmonics III.
You can edit: Portamento, Repeat, Vibrato: Speed/Depth, Attack Control, Sustain Control, Harmonics Control, Traveler Control (= filter cutoff), Pitch Bend, Forte, Volume. There is also avery unique chromium rod 'touch bar' that runs the length of the keyboard in front of the keys to control: Repeat, Forte, Pitch, Vibrato, Portamento.