Amplifiers, and Accessories
    The Lesley speaker was originally designed for electric organs, to give them the sound of the old air powered organs. For hundreds of years, organs had been powered by air, escaping from tuned pipes. The keys worked levers, which opened valves, letting the air through the appropriate pipe. The air for this came from pumps, sometimes worked by assistants, but generally operated by a set of pedals at the organists feet. air produced this way did not remain at a steady pressure, or velocity, but varied somewhat as it went through the pipes. Since the pumps were worked by regular, rhythmic motions of the organists feet, or the arms of the assistants, the organ developed a distinctive, regular waver. This waver became as characteristic of the sound of the organ, as the twang of the banjo, strum of the guitar, or scrape of the violin. When electric organs came out, with their regular, unflinching sound, they didn't quite sound like the real thing. In those pre digital days, there was no easy solution, from an electronic standpoint.
    The speaker unit itself contains a rotating solid metal plate with an opening. This plate is situated directly in front of the speaker cone.

    Though designed for organs, and meant to produce a more traditional sound, the Lesley was soon discovered by musicians looking for a novelty. When a guitar was played through a Lesley speaker, it sounded like nothing that had been heard before. There was a foreign abstract sound, which suited much of the music being performed in the sixties very well.

    A similar, though less distinct, sound can be made by throwing stereo tracks in and out of phase, a trick that was used in some recordings. This was used in much of the psychedelic music of the sixties, and seventies. The out of phase sound gave a similar quality to the Lesley sound, but did not have the rhythmic, regular effect of the Lesley. The Lesley also had the advantage of creating the effect through a single speaker, as a single sound, rather than depending upon the interference of out of phase sound waves to produce it through random interaction.

    Much of what the Lesley does, can now be done electronically, though not with the same flavor. It is also certainly easier and more practical, during a live performance, to have the speaker do the job, than set up digital amplifiers, sound proccesors, and maybe a computer, to do the ame job (cheaper too).