In order to help keep costs down, cheaper hardware was used.
The switches, potentiometers and knobs were the same as the Pro-One variety,
and a membrane switch-pad was used for program selection and 165arpeggiator and sequencer control.
The keyboard was from a Japanese company, Matsushita/Panasonic,
and it used conductive rubber pads under each key instead of J-wires.
It was a more reliable and cost-effective keyboard than the Pratt-Read J-wire keyboard.

ソース：The Prophet from Silicon Valley: The Complete Story of Sequential Circuits
P165〜P166