Wikipedia
The Rock-Si-Chord (sometimes incorrectly referred to as Rocksichord or Roxichord) is an electronic keyboard invented in 1967 to approximate the sound of the harpsichord.
As its name suggests, it was intended primarily for use in rock music, where a standard acoustic harpsichord would be drowned out.
The Rock-Si-Chord, manufactured by Rocky Mount Instruments (RMI), a division of Allen Organs Inc, was a solid-state instrument using one or two transistor oscillators per key, and was the first example of a type of instrument generally known as the electronic piano (contrast electric piano). Later RMI instruments also included piano sounds.
The prototype Rock-Si-Chord gave the Philadelphia psychedelic rock band The Mandrake Memorial their signature sound.
Composer George Crumb specifies the use of an electric harpsichord in his 1968 composition "Songs, Drones, and Refrains of Death"; however, he does not specifically call in the score for a Rock-Si-Chord, and thus it could also refer to a Baldwin Combo Harpsichord, an electromechanical instrument dating from the same era.
Around the same time Terry Riley used a Rock-Si-Chord, among other keyboard instruments, in his piece " A Rainbow in Curved Air" (1969).
Orchestrator Jonathan Tunick used a combined Rock-Si-Chord/Electric Piano in the Stephen Sondheim musical Company (1970). He considers the instrument now obsolete and recommends the use of a current electric keyboard.
Later notable examples include the 1990s band Quasi, but it has also been used in jazz (by Call Cobbs, Jr. and Sun Ra).