Yamaha DX7 II FD Reference Manual page 21

Level The level parameter is described in Output Level Button- Part 1 above.
Bp The Bp (break point) parameter determines which key serves as the boundary between the
right and left sections of the keyboard. The operator output levels of notes to the right of
the break point are scaled according
to
the right curve and depth settings. Notes to the left
of the break point are scaled according
to
the left curve and depth settings.
A -
1 Break point is located at A -1.
C8
Break point is located at C8.
Setting this parameter is the first step in determining the keyboard scaling for a voice. The
keys near the break point will be least affected by the keyboard scaling, and will therefore
produce the fundamental timbre and volume of the voice on which you are working.
Lc/Rc The right and left scaling curves determine whether the selected operator's output level
will increase or decrease as keys to the right or left of the break point are played. In
addition, the scaling curves describe how the output level will change as different keys are
played. The
Lc
(left curve) and Rc (right curve) parameters can each be assigned the
following values.
-1
i
n Level will decrease linearly with increasing distance from the break point.
-exp Level will decrease exponentially with increasing distance from the break
point.
+
1
i
n Level will increase linearly with increasing distance from the break point.
+ex p Level will increase exponentially with increasing distance from the break
point.
The negative curves decrease the output level as the distance from the break point
increases. The positive curves increase the output level in a similar manner. The linear
curves produce a more radical change in the output level than the exponential curves,
which correspond more closely to the way in which we perceive sound. Exponential
curves are therefore better suited to simulate natural volume and timbre changes found in
acoustic instruments, while linear curves produce a more extreme effect.
Mter determining the break point, the right and left scaling curves should be selected.
Consider whether you want the volume or timbre to become stronger (positive curve) or
weaker (negative curve), in which direction (left or right of the break point), and with
what type of scaling (exponential for more natural sounds, linear for more extreme
effects).
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