Michael Kac

These photos depict a prototype RMI Rock-Si-Chord that belonged to Michael Kac of the 1960s rock group Mandrake Memorial. He can be seen playing it in the only surviving live footage of the band, which is available on YouTube here. The keyboard was up for sale on eBay in 2023. The seller says they bought it from a local musician's estate. The shape of the keyboard is uncharacteristic of later Rock-Si-Chord models.

Record Collector Magazine had this to say about the band's first album and use of the Rock-Si-Chord:

The quartet quickly gained a following in Philadelphia, and were able to develop a distinctive sound when a representative of Rocky Mountain Instruments asked if they’d be interested in using a prototype of a new electric harpsichord they were hoping to market, the RMI Rock-Si-Chord. As Kac has since put it: “We realized immediately that it gave us something nobody else had.” Despite that break, they had their share of adversity over the course of 1967, before the tide began to turn their way following a support slot with The Strawberry Alarm Clock. Though they’d recently had a No. 1 hit with Incense & Peppermints, The Mandrake Memorial blew them off-stage, greatly boosting their reputation in the process.

Having signed to the small Poppy label, their likable debut appeared the following spring (featuring prominent Rock-Si-Chord, as Rocky Mountain Instruments were doubtless pleased to note). Reviewing them as support act for The Turtles at Steve Paul’s Scene club in New York on 18th September 1968, Billboard called them “a very different group with an unusual presentation”, adding that “their performance has one number drift into another, sometimes with fine transitional music by Michael Kac on keyboard.”

Craig Anderton, singer of the Mandrake Memorial, said the following about the Rock-Si-Chord in an online forum:

My band Mandrake had the first prototype Rock-Si-Chord, and it was an essential part of our sound. This is probably the best example of it being used on a song. It's from 55 years ago, and yes, that's me on guitar :) The song after "Next Number" starts out with the electric piano sound that the Rock-Si-Chord also had. I believe these were the earliest recordings of both sounds, and probably, the only ones because this was before they went into full production. The later Rock-Si-Chords didn't sound as good to my ears as those early prototypes.

RMI also made kickass keyboard amps. I started using them on guitar, I liked the flat-response/full-range behavior. I stopped using conventional guitar amps in 1968 and went through FRFR keyboard amps, and getting my sound before it hit the amps. Also I doubled between guitar and keys, and it was easier to get the guitar to sound right through keyboard amps than it was to get synthesizers sounding right through guitar amps.