The Kyma Language for Sound Design, Version 4.5

Formants
Picture a sine wave added to a delayed version of itself. If the delay time is equal to the amount of time it
takes to complete one cycle of the sine wave, the delayed sine wave will reinforce the original sine wave.
If the delay time is one-half of one cycle, adding them together will completely cancel them out. To prove
this to yourself, play a delay is a filter, and experiment with different delay times. Then play different
delays cancel different freqs to see how different frequencies are affected by the same delay time.
Now picture lots of sine waves bouncing around inside a violin or inside your vocal cavity. Because the
reflections are delayed and then added back to the original source, the same thing happens inside your
head as happens in the delayed sine waves experiment we just did: some frequencies are boosted and
others are attenuated. These characteristic boosts and attenuations in the spectrum are called formants,
and they tend to be independent of the fundamental frequency of the sound, acting more as a fixed filter
on the basic glottal pulse (which can change wildly in frequency).
In general, someone with a large head (an alien giant, for example) will have lower frequency formants,
and someone with a tiny head (say, a munchkin) will have higher frequency formants. So, if you move
the formants without changing the fundamental frequency, you can make a voice more menacing and
dangerous-sounding by lowering its formants or make it more cute and less dangerous by raising its
formant frequencies. Prove this to yourself by playing low menacing (SID6.7) § and munchkin and talking
into the microphone. You feel like saying different things through the low menacing voice than you do
through the munchkin voice.
Play shift formants and experiment with the !Formants fader. The Sound called female shift formants
does a similar thing but to a live input. In both cases, this technique performs a spectral analysis of the
voice, uses the SpectrumFrequencyScale to raise or lower the frequencies while leaving the formants in
the same place, and then uses a ScaleAndOffset to scale both the frequencies and the formants back up to
the original fundamental frequency.
Next try ring mod voice. This one also works on live input and uses single sideband ring modulation to
accomplish a similar result.
Yet another way to accomplish a similar result is use the Vocoder. Try shift formnts (vocoder). Like the
other examples, this one shifts the formants without changing the fundamental pitch, but in this case the
pitch is a monotone, because it is supplied by a sawtooth oscillator.
Synthesizing Formants
You can also synthesize formants (rather than shifting around the ones that are already there) using the
TwoFormantElement or the FormantBankOscillator. Try playing crossfade formant filter params, and
experiment with the !Vowel fader. Double-click on crossfade formant filter params to see how it is constructed.
The idea behind it is that a spectrally rich signal is fed into two filters which are combined in
parallel. More specifically, in this Sound, a sawtooth oscillator feeds into two TwoFormantElements
named formants 1 & 2 and formants 3 & 4. The outputs from these two formant filters are added together
in a Mixer called 4 formants. Then the Mixer is fed into a MIDIMapper in which !Vowel is mapped to
the range of 0 to 7 and a grid size or step size of 1.
Double-click on formants 3 & 4 to see how its parameters are controlled. The frequency of Formant1 is
((!Vowel of: #(2450 2300 2450 2550 2400 2200 2150 2200)) smooth: 0.25 s) hz
and its amplitude is
((!Vowel of: #(-12 -8 -16 -26 -29 -16 -12 -19)) smooth: 0.25 s) dB
§ This example was used by Francois Blaignan to process the voice of SID 6.7 in Paramount Picture's Virtuosity while
Francois was still at Serafine Sound Design. Francois has since gone on to start his own sound design studio and
has become the cross-synthesis guru of Hollywood.
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