Roland VK-8 Owner's Manual page 30

Playing the Organ
[SLOW] (Slow Percussion) button
Switches the speed at which the percussion sound will decay.
Button
Lit (ON)
Dark (OFF)
fig.01-25
Fast Percussion
Volume
Short decay time
Percussion on a tone wheel organ (Single Trigger
Algorithm)
The percussion on tone wheel organs did not apply to all notes that were played.
It was applied only to notes which were played simultaneously from a condition
where no notes were being played. When notes were played legato (smoothly and
connectedly), percussion was applied only to the first-played note. When notes
were played staccato (articulating each note separately), percussion was applied
to all notes. This method is referred to as single trigger algorithm, and is a very
important element in organ performance. On tone wheel organs, percussion was
produced by an analog circuit. For this reason, when there was only a very short
time interval from when one key was released until the next key was pressed, the
percussion circuit was unable to recharge fully, causing the percussion to sound at
a lower volume. The VK-8 simulates this behavior, and also allows you to modify
the organ voice settings to adjust the recharge time characteristics of the circuit (p.
51).
30
Explanation
The percussion sound will disappear slowly. The percus-
sion will have a more gentle attack.
The percussion sound will disappear quickly. The percus-
sion will have a sharper attack.
Volume
Percussion
Time
Slow Percussion
Long decay time
Percussion
Volume of the
harmonic bars
Time
You can specify the speed at
which the percussion sound
decays (p. 51).