> Can anyone tell me how a Hammond electronic organ works?

The Hammond Organ, developed at first in the early 1930's as a modest
personal project by Laurens Hammond, ended up being the principle
product of the Hammond Clock Company by the end of that decade.  It
has two important developments, with a host of technical tweaks that
on close examination are nothing short of brilliant.

The first development was the use of tone wheels as tone generators.
This was not original, but an extension of the Telharmonium, a device
used in the first decade of the century to provide music to buildings
in Manhattan.

In the Hammond, there are three shafts, driven by gears from a
synchronous (clock) motor.  Since a purely synchronous motor cannot
start itself (it only makes torque when running at the proper speed)
there is an auxiliary shaded-pole "starting" motor to get the whole
assembly up to speed.  This is why there are separate "start" and "run"
power switches.

Each of the shafts contains something like 36 "tone wheels".  These are
steel disks with crenelated edges.  Each tone wheel has a magnetic coil
pickup.  As the disk spins near the pickup, it generates a current in
the pickup coil of a frequency determined by the rate at which the
crenelations pass the pickup core.  By using mechanical frequency
generation locked to the power line frequency, Hammond organs never
go out of tune.

The second development is tonal synthesis.  Each key on the keyboard
has a nine-conductor switch.  Each note is assigned a fundamental,
two subharmonics and six upper harmonics, derived from the tone wheels.

The proportions with which these harmonics are mixed are controlled
by a set of nine "harmonic drawbars".   Each drawbar controls the
contribution of a given harmonic and has eight positions.  The number
of combinations that can be achieved is Real Big.  In the A/B/C class
of instruments, there are two (selectable) sets of drawbars plus ten
other preset stops for each manual.  The fundamental design of the
Hammond remained unchanged from 1937 to about 1975.  The modern
Hammond/Suzuki instruments use electronic synthesis.

There's a lot more, but this is a bit off-topic (although one cannot
forget the player organ, Hammond model BA).

A. B. Bonds

 [ My old dictionary suggests that the crenelated wheel is a toothed
 [ or indented wheel; c.f. French: "cre'neler", a tooth on a gear.
 [ -- Robbie