Donald James Leslie, who created and manufactured a speaker that refined the sound of the Hammond organ and helped popularize electronic music, died of natural causes September 2 in Altadena, Calif. He was 93.

Leslie was captivated with the sound of the Hammond organ when he heard it at a Barker Bros. furniture store in downtown Los Angeles, where he worked repairing radios. In the store’s large showroom, the organ, introduced in 1935, sounded much like a theater or church pipe organ.

However Leslie was unimpressed with the organ’s sound quality in the confined spaces of his home.

He began tinkering with devices to make the instrument sound more like labyrinthine pipe organs, using mechanics and electronics experience he gathered from a series of jobs.

When Leslie presented Hammond with an organ speaker he had built by hand, the company rejected it- and turned him down for a job.

Leslie later founded Electro Music in Pasadena to manufacture his speaker, which he called a Leslie speaker. It popularized electronic music during the 1940s by improving the sound of organs and keyboards, including those made by Hammond, Baldwin, Kimball, and Yamaha.

It wasn’t until the 1980s that Hammond eventually bought Leslie’s loudspeaker.

Leslie and Laurens Hammond, who engineered the Hammond organ, were inducted into the American Music Conference Hall of Fame in 2003.