Comment by phkahler

Also interesting is the electromechanical "tone wheel generator" used in the Hammond Organs:

https://forums.musicplayer.com/topic/155607-a-look-inside-a-...

91 metal wheels with lobes spinning past something like electric guitar pickups to produce sine waves. Their goal was to produce pure sine waves and then combine them via "drawbars" to produce an adjustable sound. 12 different gear ratios and different number of lobes (powers of two) to produce all the frequencies.

The rotating "Leslie" speaker was also cool, as is the electromechanical "vibrato scanner" on later models.