The Leslie speaker was invented by Donald Leslie in the late 1930s, who was working on ways to get better tremolo effects for Hammond organs. Leslie found that the optimal tremolo effect was achieved using a rotating speaker. Hammond were not interested in developing the product themselves, so Leslie marketed them as an add on for the organs. The effect was popular and became an vital tool for jazz organists, but was also used by guitarists including Buddy Guy, George Harrison and David Gilmour. In 1965, Leslie sold his business to CBS who, in 1980, sold it to Hammond - who went out of business in 1985. The Japanese Suzuki Musical Instrument Corporation aaquired both the Hammond and Leslie brands in the 1980s. Suzuki continue to manufacture Leslie speakers and Leslie branded guitar effects pedals.