Donald James Leslie (April 13, 1911, Danville, Illinois – September 2, 2004, Altadena, California) created and manufactured the Leslie speaker that refined the sound of the Hammond organ and helped popularize electronic music.
Leslie experimented with devices to, in his words, improve the sound of the Hammond organ, based on experience he gathered from other jobs, including fixing radios and one at the Naval Research Laboratory in Washington, D.C., during World War II.
When Leslie presented Hammond with his handmade organ speaker, the company rejected it. Leslie then chose to manufacture his Leslie speaker on his own. It was predominately used for liturgical and gospel church organs creating a Theatre Organ Tremulant effect. It was used with the Hammond Tone Wheel Organ as well as others in the 1940s through 1950s as well as today. The final version of the Leslie speaker is the Rotosonic drum whereas a loudspeaker is physically mounted in the spinning rotor with a narrow aperture (opening) to produce a very authentic Theatre Organ tremulant sound. It was also used in psychedelic and rock music of the 1960s and 1970s. It has since made its way into many genres of music, including pop music and jazz. It wasn't until the 1980s that Hammond bought Leslie's product to include with their organs.
- http://www.washingtonpost.com/wp-dyn/articles/A4585-2004Sep8_3.html The Washington Post, September 8, 2004, Obituaries
- http://articles.latimes.com/2004/sep/07/local/me-leslie7 Los Angeles Times, Donald Leslie, Obituary, 7 Sept. 7, 2004