The Kyma Language for Sound Design, Version 4.5

Cross Synthesis
The idea of cross synthesis is to track a parameter of one sound and use it to control that same parameter
or a different parameter in another sound. The result is the superimposition of some of the characteristics
of one sound onto another.
Simple Cross Synthesis
Double-click track freq & amp and open the signal flow graph completely by holding down the Command
or Control key while clicking on the arrow tab on the left edge of the rightmost Sound. To make it
clearer, drag the GenericSource further to the left, and position 0 cascade and spectrum for fmnt oscils so
they are not on top of each other.
Select GenericSource25 and play it. Then select track freq & amp and play it. Can you tell what is going
on (especially given that preface in the first paragraph)?
The rightmost Sound is a VCA since it imitates a “voltage-controlled amplifier” (actually more like a 4quadrant
multiplier). In actuality, all it does is multiply its two inputs — synthetic ah and boost amp env.
Follow the boost amp env thread. boost amp env itself is a Gain that boosts its input by eight times. Its
input, amp fol is an AmplitudeFollower. Double-click it to see its parameters. To read a description of
how this kind of Sound works, click on the italicized label Amplitude Follower in the lower right corner
of the parameter fields. This opens a help window containing a description of the Sound and each of its
parameters.
After you have read the description of what the AmplitudeFollower does, select the GenericSource25, and
use Full waveform from the Info menu to see how the amplitude changes over time. Leave that window
open, select amp fol, and plot its full waveform. Line up the two windows, one below the other to compare
them.
Because of the absolute value, the output of the AmplitudeFollower is all above zero. Because of the averaging,
it is a little sluggish in its reaction time. For example, at around 0.7 seconds, there is a big spike in
the unprocessed waveform (the “tch” in “virtue”), but in the amplitude envelope, this spike never gets
very large, because the AmplitudeFollower is averaging over 0.1 seconds. Try changing the TimeConstant
to one tenth of its value: 0.01 s. Then plot the output of the AmplitudeFollower and compare the
size of the spike. By decreasing the TimeConstant, you can make the envelope respond to shorter features
in the waveform. Take note of the minimum and maximum values written at the top of the
waveform window. That should explain why we needed to feed the output of the AmplitudeFollower
into a Gain before using it as an amplitude envelope on synthetic ah.
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