(Excerpted from the OriginalHammondLeslieFaq.)
Vibrato is the periodic ''raising'' and ''lowering'' of the pitch (frequency modulation), and is thus fundamentally different from ''tremolo'' which is a variation in only the ''loudness'' of the pitch (amplitude modulation). The early Hammond organs featured a [Tremolo] system however it was generally considered to not be very effective.
-The Hammond vibrato was invented by Hammond engineer JohnHanert. This vibrato is implemented using a tapped DelayLine: really a ''low-pass filter''. The signal is applied to the DelayLine and a rotating [Scanner], attached to one end of the [ToneGenerator] assembly and geared to turn 412 RPM or about 7 times a second, picks the signal off of the DelayLine at the ''tap points''. The [Scanner], a single-pole 16-throw air-dielectric capacitor switch, is wired so that the tap point will traverse the entire delay line twice, once up the DelayLine and once back down, for each [Scanner] rotation. As the DelayLine is traversed ''phase'' is added-to and then subtracted-from the signal.
+The Hammond vibrato was invented by Hammond engineer JohnHanert. This vibrato is implemented using a tapped DelayLine: really a ''low-pass filter''. The signal is applied to the DelayLine (aka LineBox)
and a rotating [Scanner], attached to one end of the [ToneGenerator] assembly and geared to turn 412 RPM or about 7 times a second, picks the signal off of the DelayLine at the ''tap points''. The [Scanner], a single-pole 16-throw air-dielectric capacitor switch, is wired so that the tap point will traverse the entire delay line twice, once up the DelayLine and once back down, for each [Scanner] rotation. As the DelayLine is traversed ''phase'' is added-to and then subtracted-from the signal.
The chorus signal is produced by adding the "dry" non-pitch-shifted signal to the "wet" pitch-shifted signal.
The three settings each of vibrato and chorus correspond to different amounts of total delay thus different amounts of total pitch shift.
In addition to the pitch shifting function, the vibrato, as implemented in the Hammond organ, also acts as a ''sweeping low-pass filter''. There is some frequency response and amplitude variation as the tap point of the filter is swept.
Provided on the organs so equipped are __vibrato__ and __chorus__ settings ''V1'',''V2'',''V3'' and ''C1'',''C2'',''C3''.
-;: ''[SpinetOrgans], at least the __M__ series, have only two vibrato/chorus depths: ''small
'' and ''normal
'' --- these correspond approximately to the '1' and '2
' settings on [ConsoleOrgans].''
+;: ''[SpinetOrgans], at least the __M__ series, have only two vibrato/chorus depths: ''normal
'' and ''small
'' (VibratoSmall)
--- these correspond approximately to the '1' and '3
' settings on [ConsoleOrgans].''
