NONLINEAR LABS C15 - 4.4 Macro Controls

Sound Generation
19
One oscillator modulating the other:
▶
First, please reload the Init-Sound. Don’t forget to turn up Level A on the
Output Mixer to [ 60.0 % ]. Both Oscillators are now generating simple sine-
waves. What you are hearing right now is Oscillator A.
▶
Press PM B (Oscillator A).
▶
Turn the Encoder and dial in approx. [ 75.00 % ].
ߊ Oscillator B is not added to the output mixer but used to modulate the
phase of Oscillator A instead. Since Oscillator B is currently generating a
sine-wave at the same pitch as Oscillator A, the audible eect is similar to
self-modulation of Oscillator A. But here comes the fun part, we are now
detuning Oscillator B:
▶
Press Pitch (Oscillator B).
▶
Sweep the Encoder and play some notes. Then dial in [ 53.00 st ].
ߊ You will now be hearing some so “metallic” timbres that sound quite
promising (but that’s only us, of course...).
߃
Excursion – The Secrets of Phase Modulation (PM) –
Oscillator Pitches and Modulation Index
When modulating the phase of one oscillator by another one at a dierent fre-
quency, lots of sidebands or new overtones respectively are generated. Those were
not present in the source signals. The frequency ratio of both oscillator signals
defines the harmonic content resp. the overtone structure of the resulting signal.
The resulting sound remains harmonic as long as the ratio between the modulated
oscillator (called “carrier” – here Oscillator A) and the modulating oscillator (called
“modulator” – here Oscillator B) is a proper multiple (1:1, 1:2, 1:3 etc).
If not, the resulting sound will become increasingly inharmonic and dissonant.
Depending on the frequency ratio, the sonic character is reminiscent of “wood”,
“metal” or “glass”. This is because the frequencies in a vibrating piece of wood, metal
or glass are very similar to the frequencies generated by PM. Obviously, PM is a very
good tool to generate sounds that feature this type of timbral character.
A second crucial parameter is the intensity of the phase modulation or “modulation
index”. In the C15, the appropriate parameters are called “PM A” and “PM B”. Dierent
values will produce radically dierent timbral results. The interaction between the
pitch of the respective oscillators and their modulation depth settings (“PM A / B”) is
also crucial to the sonic results.