Hammond P-100 Tonewheel Organ

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The P-100, which appeared in 1971 in a two-part, transportable housing, is a variant of the L-100 and the L-100 P. It was produced under licence by Jorgensen in Copenhagen.

The sound production of the Hammond organ begins in the cogwheel oscillator. Metal tone wheels with a wavy edge rotate in front of electromagnetic pickups (iron cores in coils). The waveform causes the edge of the wheel to periodically move away from and towards the iron core. This changes the magnetic field, which induces an alternating voltage in the coil, resulting in an alternating current. The shape of the wheel results in a sinusoidal oscillation. The gearwheel oscillator contains 91 tone wheels with different numbers of teeth, which are mounted on a common axle and driven by a synchronous motor via a transmission gear. As the sine tones produced in this way are not very musically appealing, several tones can be continuously assigned to each key of the manual via drawbars. The Hammond sound was supplemented by a mechanically generated reverb, a vibrato generated with rotary capacitors and electronic percussion. (source: music web.ch)