<verbatim>
(Motor RPM/60)*Teeth in Toneweel*(Teeth in Driving Gear/Teeth in Driven Gear)
-So for A-440
on a 60Hz
organ: (1200/60) * 16 * (88/64) = 440Hz
+So for the
A above middle C
on a 60 Hz
organ: (1200/60) * 16 * (88/64) = 440 Hz
-The
A notes are
the only notes
on the Hammond which agree
exactly with the
equal tempered scale
. The notes which are the farthest off pitch in the first seven octaves are the G#. They are .69 cents flat from the correct pitch. The top half octave is farther off pitch due to the number of teeth on the tonewheel not equaling 256. Using 192 teeth, generating the correct pitch from C7 to F#7 requires using the gear ratios for F through B. In the top half octave, the C# is the farthest off pitch, about 1.93 cents sharp:
+This
A tonewheel being exactly
the same frequency as the commonly accepted concert pitch standard of 440 Hz is not accidental but prescient. Historically, concert A has wandered between 430-450 Hz. Beside the Hammond, the famous Stroboconn tuner introduced in 1936 also used a synchronous motor to spin a disc that set concert A at 440 Hz. Within a couple of years, Stroboconn tuners were being used globally to tune concert orchestras. By 1939 enough orchestras had set their concert pitch to A = 440 Hz that the international concert pitch standard was established. None of the twelve semitones
on the Hammond are
exactly equal tempered. The notes which are the farthest off pitch in the first seven octaves are the G#. They are .69 cents flat from the correct pitch. The top half octave is farther off pitch due to the number of teeth on the tonewheel not equaling 256. Using 192 teeth, generating the correct pitch from C7 to F#7 requires using the gear ratios for F through B. In the top half octave, the C# is the farthest off pitch, about 1.93 cents sharp:
<verbatim>
For C#-4434: (1200/60) * 192 * (74/64) = 4440Hz
</verbatim>
