Kurzweil K2600 - MUSICIANS GUIDE REV A PART NUMBER 910330 CHAP 17 Manual page 9

input b
value
input b
value
Figure 17-5 hipass (f = a, b)
b / (1 - a)
This is another weighted difference equation similar to the Þrst six. The value of Input a is
subtracted from 1. The value of Input b is then divided by the difference. YouÕll get considerably
different results for different input values of a and b.
a(b-y)
Think of this equation as reading Òy is replaced by the result of the function a(b-y).Ó The value of
y indicates the value of the FUNÕs output signal. Every 20 milliseconds, the K2600 takes the
current value of y, runs the equation, calculates a new value of y, and inserts the new value into
the equation. Consequently the value of y will change every twenty milliseconds. HereÕs an
example. When you play a note, the K2600 starts running the FUN. The Þrst value for y is
always 0. WeÕll assume the value of Input a is +.5, and the value of Input b is +1. The Þrst time
the K2600 evaluates the FUN, the result of the equation is .5 x (+1 - 0), or .5. So the FUNÕs output
value after the Þrst evaluation is .5. This becomes the new value for y, and when the K2600 does
its next evaluation of the FUN, the equation becomes .5 x (+1 - .5), or .25. The resulting output
value is .25, which becomes the new value for y. For the next evaluation, the equation is .5 x (+1-
.25), or .375.
(a + b)^2
The values of Inputs a and b are added, and the result is squared (multiplied by itself). This will
change the linear curve of a unipolar control signal into a curve thatÕs lower at its midpoint (by a
factor of 2). Bipolar control signals will generate curves that are high at both ends, and 0 in the
middle.
input b
value
time
1) 2)
3) 4)
input b
value
time
FUNS
The FUN Equations
time
time
17-9