Complex Tone Wheels

In patent 2,508,514, granted 23 May 1950, J. M. Hanert describes a significant revision to the pedal tone generation system. This included wiring changes to mix some of the even harmonic tonewheel outputs with the output of the lowest octave of tonewheel and changes in the shape of the tonewheels in the lowest octave. The bottom 12 tonewheels, heard only in the pedals, are modified to produce a more complex waveform than the simple sine wave previously used in this octave. These tonewheels are cut with a two flat sides on opposites sides of the tonewheel. This generates a "complex tone comprising a fundamental and a series of odd harmonics of progressively decreasing amplitude". The resulting output is very similar in the shape of a square wave. When the odd harmonics of these tonewheels are mixed with the even harmonics generated by