Leslie Model 21H

Don Leslie loved the (then) new Hammond Organ, but found the tone a little “square’. He wished the Hammond to sound more like his beloved “Mighty WurliTzer” Theatre Pipe Organ. Being a seasoned and skilled inventor, he imagined utilizing a principle called the “Doppler Effect”-(It’s why a train whistle seems to go down in pitch when a train passes you). Don took a horn speaker, and developed an apparatus to make it spin around in a circle. Legend has it Don constructed the whole thing in a closet! His experiment bore fruit-The spinning horn gave the Hammond Organ what is called in the pipe organ world, a “tremulant”. Vibrato, Tremolo, and a little “whoosh” of air all put together. It made the Hammond Organ sound completely different. The Hammond’s life in all popular music-Jazz, Rock, Pop was born at that moment, and Don Leslie secured his place in the rare pantheon of immortal inventors. Leslie speakers cabinets built from 1951 to 1958 are marked 21H.This particular cabinet has the Serial number of 16209.

Leslie Model 21H Service Manual