3.5

660MainStage Instruments
Because the speakers rotate toward the front of the cabinet (the listening position), then
toward the back of the cabinet, you hear a “Doppler effect”—where sounds become louder
and brighter as their position changes. To give you an idea of this effect, it is much like the
sound of a train going past if you were standing on the platform. On approach, the sound
is muffled, but then it becomes both louder and brighter as the train passes, and finally it
becomes more muffled as it moves away from you.
The rotating driver/sound baffle can be switched between two speeds—fast/Tremolo or
slow/Chorale (or stopped completely with a mechanical brake). The transition between
the two speeds, or the use of a fixed speed, produces the characteristic “Leslie” vibrato,
tremolo, and chorus effects.
The first Leslie, the model 30, had no Chorale—just tremolo and stop. The Chorale idea
(which came much later) was born of a desire to add a vibrato to the organ. Chorale, which
offers far more than a simple vibrato, was first introduced to the market with the 122/147
models. At this time, Leslie also added the “Voice of the pipe organ” label to his cabinets.
It wasn’t until 1980 that the two companies and brand names came together, six years after
the last tonewheel organ was built. Mechanical Leslie rotor cabinets are still being built
today, by the Hammond-Suzuki company.