This is another attempt to produce a constant frequency: a 7805 voltage regulator was driven from the variable voltage from the generator. The 5 Volt signal was used to drive a motor with a disk mounted on it.
The idea was that the disk would spin at a fixed frequency and various notes could be made by the paint making and breaking connections. But the drag from the brushes was too large. Perhaps instead, an optical approach will be tried, or if all fails, microcontrollers used.
One interesting possibility with the disk is that alternate disks can be used with different scales. Here, disks for pentatonic, diatonic, and chromatic scales are shown.