The best-selling and most widely used instrument was the RMI Electra-piano, that was played by numerous artists in the late 1960s and early 1970s, including Steve Winwood, Genesis' Tony Banks, and Yes' Rick Wakeman.

[6] RMI had no experience in the rock and pop market, as Allen had been used to selling instruments to churches and theatres.

They produced advertisements featuring a mascot, "Gopher Baroque" and described the instrument in typical slang of the era, such as "I mean, you start swinging this axe and plastic things like crumble.

[10] The Model 400 was a console version of the 300, which was intended for the home and club market and included a self-contained speaker system.

The 140 came with a single 15-inch (380 mm) JBL woofer, while the 140A featured a pair of them, and both had a set of dual high-frequency drivers.

An optional accessory was available that was particularly good at producing high frequencies, that sat on top of the amp and was nicknamed the "Hi-Scream Cone".

It cost $4,495 and supported transposition, pitch bend, and upgradeable voices via a series of punch cards.

[16][6] It featured 48 keys and two digital harmonic generators, each supporting sixteen different sets, and was equipped with a voltage-controlled filter and octave shifter.

Other features included pitch bend, portamento, and controls for amplitude and frequency modulation.

[16] By the early 1980s, RMI was in decline owing to the high price of its instruments and competition from polyphonic synthesizers like the Prophet 5 and Oberheim OB-X.

[16] The Rock-Si-Chord quickly became popular and was used by the Beach Boys, the Lovin' Spoonful, Quasi, Sun Ra, and Garth Hudson of The Band.

[8] The Electra-piano was widely used by rock musicians in the late 1960s and early 1970s, including Deep Purple's Jon Lord, Todd Rundgren, Frank Zappa, Rick Wakeman with Yes, and in his solo albums, Tony Banks with Genesis, Ron Mael with Sparks, Nicky Hopkins, Stevie Wonder, and Elton John.

Steve Winwood played an Electra-piano solo on John Barleycorn Must Die's "Empty Pages".

Owing to a lack of polyphonic synthesizers, he ran the RMI through effects pedals in order to create new sounds.

The RMI was used for live renditions of songs that had a piano on the studio version, such as "Firth of Fifth" and "The Lamb Lies Down on Broadway".

[6] The RMI Keyboard Computer was used by Isaac Hayes on his album Chocolate Chip (1975), Wakeman, the Band's Garth Hudson, the Moody Blues' Mike Pinder, and The Enid's Robert John Godfrey.