The Mastersonic Organ was an improved tone wheel organ designed to produce more accurate pipe organ sounds. The designers, John Goodell and Ellsworth Swedien, discovered that if they shaped the tone-wheel ‘pickups’ they could induce tones with different ‘natural’ harmonic content – rather than attempt to create a pure sine wave and artificially colour it as in the Hammond Organ. To achieve this the Mastersonic had individually shaped magnets for each tone wheel sound; a “string” magnet, a “flute” magnet, a “diapason” magnet, and so on.
“…There were twelve shafts with seven pitch wheels each which rotated near the irregularly shaped magnets wound with coils. Each of the pitch wheels contained twice as many rectangular teeth as the preceding one, so seven octaves were produced per shaft. Several differently shaped poles were dispersed radially around each wheel.”
Alan Conway Ashton electronics, Music and Computers
Each tone-wheel was shielded against magnetic interference from the other, adding to the bulk and complexity of the instrument. The instrument was controlled by a seven octave special keyboard, designed to simulate attack envelopes. The resulting sound was indeed a much more accurate pipe organ sound but at the expense of size; the Mastersonic was a huge, complex and expensive machine and few were built or sold.
Sources
‘Microsound’ Curtis Roads MIT 2001
ELECTRONICS, MUSIC AND COMPUTERS. Alan Conway Ashton. December 1971 UTEC-CSc-71-117