Motorola Scalatron

The Motorola Scalatron was an early electronic microtonal keyboard instrument conceived by Herman Pedtke and developed by Motorola in the early 1970s. The earliest model was essentially a retunable electronic organ with two five-octave keyboards, each keyboard having only 12 pitches per octave. Each chromatic note could be tuned by means of binary switches on the instrument, from among 1024 pitches, with all octaves tuned alike. The switches for the notes in a central octave (from A to G#) were set with the aid of a computer printout that lists all of the possible pitches within a range of 218.6 to 436.8 Hz. Since the two keyboards could be tuned independent of one another, this allowed playing music with up to 24 pitches per octave. Motorola made only about 20 in total, costing around $6,000 to $10,000.

Subsequent innovations suggested by George Secor include the addition of synthesizer functions, as well as the application of a "new" generalized keyboard layout with a hexagonal arrangement of keys, better suited to the playing of microtonal music:

"“Earlier that year (1974) I had attended a demonstration of the Scalatron (digitally retunable electronic organ) prototype, and recognizing that conventional keyboards were not the best way to perform music with more than 12 tones in the octave, I unwittingly proceeded to re-invent the Bosanquet generalized keyboard and subsequently approached the Motorola Scalatron company with the proposal of employing it on their instrument.”… “Around that time several members of the xenharmonic movement had gotten in touch with Scalatron president Richard Harasek and sent him copies of the first two issues of Xenharmonikôn, which he passed on to me and which I promptly read. The second issue included Erv Wilson’s diagrams of a modification of Bosanquet’s keyboard, with hexagonal keys, at which point it became clear that my keyboard proposal was not new… For the remainder of the year I was heavily involved in the generalized (Bosanquet) keyboard Scalatron project and, after that, in using it to explore new tunings. In effect, the keyboard that I had discovered was destined to be overshadowed by the one that I had rediscovered.”"

- George Secor Three Scalatrons were produced with the generalized keyboard, two allowing 31 pitches (50 keys) per octave and the third allowing 56 pitches per octave. George Secor briefly toured with one of these instruments, playing works by Harry Partch, Ben Johnston, Ivor Darreg, and others.

The generalized keyboard layout was originated by Robert Bosanquet around 1875 and independently invented by George Secor a century later.