The Kyma Language for Sound Design, Version 4.5

SyntheticSpectrumFromSounds
Spectral Sources Category
Generates a synthetic spectrum whose amplitudes, frequencies (and optionally, bandwidths) are
controlled by two input Sounds. One input supplies the amplitudes and the other supplies the
frequencies (optionally alternating with bandwidths). You can think of each cycle of the input Sounds as
defining one frame of the spectrum. If the input Sounds change from cycle to cycle, then the spectrum
will also change from frame to frame.
A SyntheticSpectrumFromSounds (like other Sounds in the Spectral Sources category) outputs spectral
envelopes in the following format:
Left Channel: Amp1 Amp2 ... AmpN
Right Channel: Freq1 Freq2 ... FreqN
For each frame, Amp1 is the amplitude of the first partial (and Freq1 is the frequency or pitch of the first
partial), Amp2 is the amplitude of the second partial (corresponding with Freq2), and AmpN is the
amplitude of the highest numbered partial (specified in NbrPartials). Then the whole sequence repeats
for the next frame of the spectrum. Because of this repetition rate, the output of the
SyntheticSpectrumFromSound has a kind of periodicity to it, where the period is the equal to the same
number of samples as there are partials in each frame.
Amplitudes
If the period of this Sound in samples is equal to NbrPartials, then one cycle of this Sound defines one
frame’s worth of amplitudes for the synthesized spectrum. (For example, to synthesize 80 partials, set
the Frequency of this Sound to 80 samp inverse if you want the cycles to line up with frames). If the
repetition rate of this Sound is lined up with the number of partials in each frame of the spectrum, then the
waveform of each cycle of this Sound will correspond to a kind of spectral envelope for each frame of the
spectrum. For example, if you select ExponRev as the waveform of an oscillator whose period is 80
samples and set NbrPartials to 80, then each frame of the spectrum will have high amplitudes on its
lower-numbered partials and lower amplitudes on the upper partials. Even more interesting is to make
this Sound’s frequency adjustable within a narrow range so you can create spectral envelopes that "drift"
because their repetition rates are slightly out of phase with the number of partials being generated on
each frame.
FrequenciesAndBandwidths
If the period of this Sound in samples is equal to NbrPartials, then one cycle of this Sound defines one
frame’s worth of frequencies (or pitches i f you have LogScale checked) for the synthesized spectrum.
(For example, to synthesize 80 partials, set the Frequency of this Sound to 80 samp inverse if you want
the cycles to line up with frames). If the repetition rate of this Sound is lined up with the number of
partials in each frame of the spectrum, then the waveform of each cycle of this Sound will provide the
frequencies for each partial in one frame of the spectrum. For example, if you select Ramp as the
waveform of an oscillator whose period is 80 samples and set NbrPartials to 80, then, in each frame of
the spectrum, the lower-numbered partials will have low frequencies, and the higher-numbered partials
will have high frequencies. Even more interesting is to make this Sound’s frequency adjustable within a
narrow range so you can create spectra that "drift" because their repetition rates are slightly out of phase
with the number of partials being generated on each frame.
If the SyntheticSpectrumFromSounds is controlling something that requires bandwidth (like
FormantBankOscillator or VocoderChannelBank), and you have checked the SendBandwidths box, then
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