Vad är principen för en hammondorgel? Några metallgrejer som snurrar runt?
Så här förklarar engelska wikipedia det hela. Vet inte om jag förstår det...
"The tonewheel assembly consists of a synchronous AC motor and an associated gearbox that drives a series of rotating disks. Each disk has a given number of smooth bumps at the rim; these generate a specific frequency as the disk rotates close to a pickup assembly that consists of a magnet and electromagnetic coil.[footnotes 1]
As each bump in the wheel approaches the pickup, it temporarily concentrates the magnetic field near it, and thus strengthens the magnetic field that passes through the coil, inducing a current in the coil by the process of electromagnetic induction. As the bump moves past, this concentrating effect is reduced again, the magnetic field weakens slightly, and an opposite current is induced in the coil. Thus, the frequency of the current in the coil depends on the speed of rotation of the disk and the number of bumps."