The Kyma Language for Sound Design, Version 4.5

You can read these settings, but you can’t modify the text, at least not by typing. The only way to alter
this parameter is to change the settings of the faders in the virtual control surface, and to then press the
button labeled Set to current event values found just below the EventValues parameter field.
Proceeding ever leftward, let’s next double-click the module called LPF. If you don’t see a module to the
left of 3 filtered saws, click on the small tab attached to the center of the left edge of the 3 filtered saws
icon. This little tab with a right-pointing arrow in it indicates that a Sound has hidden. Click on the tab to
show the Sound’s immediate inputs. Click again to hide the inputs of a Sound. To display all of the inputs
of a Sound (i.e. all of its immediate inputs, the inputs to those inputs, etc.), click the tab while holding
down the Control or Command key. You can use these tabs to keep your signal flow graphs uncluttered
and easy to read, while still being able to edit any part of the graph when necessary. (See Editing the Signal
Flow Diagram beginning on page 26 for more information about using the signal flow diagram.)
Here we get our first glimpse of some of the red Event Values we were controlling from the virtual control
surface. This is a generic filter that you can set to lowpass, highpass, or allpass. This particular filter is
set to lowpass, so it will tend to attenuate all frequencies in its input that are above the value in the Frequency
field. The other parameters tell us that this is a fourth order filter and that an Event Value called
!Feedback controls a parameter similar to the “resonance” control of analog filters. When you were experimenting
with the faders in the virtual control surface you probably noticed that you could make the
filter ring or even blow up by increasing the value of !Feedback.
The expression in the Frequency field
filter cutoff L * (!Cutoff * 11050 hz + 200 hz)
indicates that, depending on the setting of !Cutoff, the maximum Frequency value will be between
200 hz and 11250 hz. This maximum value is in turn multiplied by a Sound called filter cutoff that generates
an envelope shape.
To see how the envelope shape controlling the filter cutoff is generated, double-click the icon named filter
cutoff. This is an ADSR (Attack time, initial Decay time, Sustain level, Release time) envelope generator.
From the parameters we can tell that when the envelope generator is triggered by a MIDI key-down
event, it goes from 0 to maximum amplitude with 10 milliseconds, drops to 75% of its maximum amplitude
in the next 10 milliseconds, where it remains for as long as the key is held down, after which it drops
back to zero in 5 seconds starting from when the key is released. So, as you already heard when you were
experimenting earlier, each time you press a MIDI key, the filter opens up to allow more high frequencies
to pass through, and when you release the key, the filter closes back down again.
What input is LPF filtering? Double-click the icon called phatness. This is a Gain module that is set to
multiply the amplitude of its input by ten. In this case, since the input is already a full-amplitude signal,
the effect of the Gain will be to distort the signal by clipping it, turning it from a sawtooth-like waveform
into more of a square-shaped waveform, and as a result, changing the timbre from something with all
harmonics to something with only the odd harmonics.
To see and hear this for yourself, select phatness and choose Oscilloscope from the Info menu. Leave all
the other faders at zero, and type 0.01 into the field above the !Volume fader (and hit Enter). Then play
some low pitches on the keyboard. Gradually increase !Volume using the fader until you see and hear
the waveform flatten out at the top and bottom because it hits the maximum amplitude. Notice that
changing !Volume changes not just the loudness, but the timbre as well.
To see how the spectrum is affected, make sure phatness is still selected, and choose Spectrum analyzer
from the Info menu. ‡ Hold down C 6 on your keyboard (two octaves above middle C), and alternate the
position of the !Volume fader between almost zero and almost one by clicking with the mouse towards
the bottom and then towards the top of the fader. Notice how every other spectral line disappears when
the signal is clipped? Try this a few times, listening to the change in timbre that accompanies this change
in the spectrum. There is another, more subtle effect you can observe on the spectrum: as soon as the
waveform is clipped, it has an infinitely sharp corner on it, and infinitely sharp corners have an infinite
number of harmonics, so some of the short lines you see clustered around the harmonics are actually ali-
‡ By the way, this explanation is not essential to understanding and using Kyma — it is just an interesting aside.
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