Donald Leslie created and manufactured the rotary speaker, which people also know as the Leslie speaker. This device refined the sound of the Hammond Organ and revolutionized electronic music. Leslie also invented a special speaker which intended to improve the sound of the Hammond Organ. This speaker rotated itself inside its own cabinet.
The Theater Organ Tremulant Effect and the Rotary Speaker
The rotary speaker generated a Doppler effect that modulated sound and mimicked the resonance of the Hammond Organ in a large space. The rotary speaker was first used for the electronic reproduction of organ instruments, including gospel and church organs. The device created a Theater Organ Tremulant effect. Afterwards, the Rotosonic drum became the final version of the Leslie speaker. In particular, experts mounted this in a spinning rotor that had a narrow opening. The, the result was a Theater Organ Tremulant sound. Rock and psychedelic music often used it. Nowadays, a variety of music genres, such as pop and jazz, include it frequently.
The Doppler effect can alter the sounds perceived by the human ear. Similarly, the directional peculiarities of the speaker and the phase effects caused by air turbulence influence too. In this scenario, one speaker and another one in the opposite direction perform both the pitch modification and the intensity variation.
The Leslie Speaker as an Effect
Rotary loudspeaker effect simulation uses a combination of modulation and delay line modulation. The simulation uses the aforementioned modulated delay line for pitch modifications. In addition, it uses the amplitude modulation for intensity modifications. You can achieve a directional sound by modulating the amplitude of both the output signal and the delay lines. This modulation occurs at the same time as the delay one.
At the return point, the pitch remains unaltered and the amplitude at its minimum level. The user achieves a raised pitch and an increasing amplitude with a slight movement directed towards the listener. A human ear can perceive a stereo rotary speaker because of an unequal mixing of two delay lines to the sides of the channel output.
Rotary Speaker: Final Notes
The sound produced by the rotary speaker becomes more lively with the presence of amplitude, pitch modulation, and spatialization. When the rotation speed is lower, the sound is similar to the echoes produced inside a cathedral. Opposite to this, when the rotation speed is higher, the sound is almost close to a ring-modulation effect.
If the rotary speaker interests you, you can look for other devices that follow its mechanic, such as rotary woofers.
