image from Steiner Parker product literature courtesy of Kevin Lightner

The Steiner-Parker Multiphonic Keyboard is a 49-note (C-C) analog controller keyboard with what Steiner-Parker describes as "multiphonic" capabilities. It is actually one of the first arpeggiators. It had a large panel to the left of the keyboard which contained all of the controls. If you hold more than one note down It would alternate between the notes you hold down. I could be set to arpeggiate up, down, or random. The speed could also be set as well as single or multiple triggering. With external triggers it could be used as a chromatic scale sample and hold.

[from The A-Z of Analogue Synthesizers, by Peter Forrest, published by Susurreal Publishing, Devon, England, copyright 1994 Peter Forrest]