A tremulant loudspeaker for use with electronic organs, designed by Donald J. Leslie (b c1911) and manufactured from 1940 by the Electro Music Co. in Pasadena, California. Since 1965 the company has been bought by CBS Musical Instruments, the Hammond Organ Co. (1980), Noel Crabbe (1985; licensed to Calo Corp., Batavia, near Chicago, in 1988) and Hammond Suzuki USA (1992); it is now based in Addison, near Chicago. The firm has marketed many models, originally intended only for Hammond organs but subsequently also for other types, in addition to licensing individual manufacturers (including Baldwin, Conn, Gulbransen, Kawai, Kimball, Kinsman, Lowrey, Thomas and Wurlitzer organs, as well as the Rhodes electric piano). In the digital age, several companies have manufactured electronic Leslie simulators, including Dynacord, Korg and Voce, and equivalent circuitry is also built into various electronic organs. Since the 1960s musicians have also used Leslie loudspeakers with other instruments, particularly electric guitars; special preamplifiers were manufactured for this.
The Leslie is normally housed in a separate cabinet, controlled remotely from the organ console, but in some instruments it is incorporated into the console. The sound is diffused from fixed loudspeakers, through a treble unit with rotating twin horns (one is a dummy, for balance) and a rotating curved reflector for the main loudspeaker (itself rotated in several models); both have two speeds, slower for chorus and faster for vibrato.
M. Vail: Don Leslie: the Whirl to Success, Keyboard, xvi/4 (1990), 1212; continued as The Leslie Speaker, Part 2, xvi/6 (1990), 879; rev. in The Hammond Organ: Beauty in the B (San Francisco, 1997), 1215, 13059
HUGH DAVIES