If you attend performances of jazz, rock, gospel, country, and other genres, you will likely hear the Hammond B3 organ. Not many listeners know that instrument by name, but they would easily recognize its sound in many genres of music. The Hammond Organ was developed in 1935, by a clock maker Laurens Hammond. Evantually, he set up his Hammond Organ Company in Evanston, Illinois. The Hammond B3 was the most common version of the instrument that is found in popular music. Other variations were made for churches and concert halls.
Hammond organs could be equipped with a Leslie Speaker, which rotated at different speeds. Rotating slowly the sound seems to be moving in waves of space. Rotating fast, the effect was a gradually increasing vibrato that was one of the unique qualities of the Hammond sound. Another effect was reverb, which was created by a spring that would pull away from the magnet when a key was released. The effect was a short fade after each note that sounded like an echo, instead of an abrupt end to the sound, without the reverb. This straightforward idea was copied by many sound designers and became widely used in other keyboard instruments and for microphones and electric guitars, to name only a few.