Leslie was born on April 13, 1911 in
Danville, Illinois. His father was Benjamin Franklin Leslie, and his mother was Lucy Keller Leslie. His family moved to
Glendale, California in 1913, where Leslie attended school, graduating from
Glendale Union High School in 1929. He was very interested in
piano and
pipe organ music. Leslie learned about mechanics, electronics, and
radios while working various jobs, and by the mid-1930s he was working at
Barker Bros. in Los Angeles as a radio service engineer. Barker Bros. sold and repaired the newly-introduced Hammond organs, and Leslie bought one in 1937, hoping it would be a suitable substitute for a pipe organ. When he heard the organ's sound in his home compared with the spacious showroom where he originally heard it, he was disappointed. To Leslie's ear, in a confined space the sound had no resonance, and the pure electronic oscillators sounded "dull, shrill, and still." He set out to design an
organ speaker to remedy this problem, experimenting with various designs over the next four years, and eventually concluding that a design that combined a fixed
speaker with a rotating baffle chamber inside its
cabinet, which produced a
tremolo effect with a variation in pitch, producing a sequence of
frequency modulated sidebands, achieved the sound effect he desired. In 1940, Leslie, hoping for a job with the
Hammond Organ Company, demonstrated his prototype at the company's Los Angeles retail store, with Laurens Hammond listening in from Chicago by telephone. Hammond, which already offered its own speaker (the Hammond Tone Cabinet), did not appreciate the effect offered by Leslie's speaker design, and declined to manufacture or market it. In 1941, Leslie founded Electro Music in Pasadena, California to manufacture and market the speaker, which he named the Vibratone 30A. Leslie assembled the speakers himself in his garage. He produced speakers under various names before settling on Leslie as the universally accepted name by 1949. Also in 1949, Leslie was granted a patent for his "rotatable tremulant sound producer," In 1965, Leslie sold Electro Music to
CBS, which made it a part of
CBS Musical Instruments. In 1980, seven years after the death of Laurens Hammond, the Hammond company bought Electro Music and the Leslie brand from CBS, with Donald Leslie remaining involved with the business until 1985. Leslie was inducted into the American Music Conference Hall of Fame in 2003. ==Personal life==