Make Noise STO - Manual (Page 7)

FM, SYNC and Variable SHAPE:
The STO is capable of generating harmonically rich waveforms. This is accomplished through the modula-
tion of the Variable SHAPE, FM and Oscillator SYNC.
Linear and EXPO FM
Frequency Modulation super-imposes the frequency of one oscillator upon another. The result is that the
oscillator that is FM'd will carry the modulating oscillator's pitch information in the form of harmonics. Linear
FM attempts to preserve the base frequency of the carrier oscillator allowing for harmonically rich waveforms
to be generated while still being able to track the 1V/ Octave scale properly. The Linear FM input is AC
coupled and has a Level control. As you increase the Level, the Amplitude of the signal Frequency Modulat-
ing the STO is increased and the resulting signals at all outputs of the STO will become increasingly more
complex. At greater than 80% Level, the Linear FM bus goes into overdrive and the STO will not track accu-
rately.
Exponential FM is also possible with the STO by patching your modulating oscillator tot he EXPO input. You
will want to patch a VCA such as the Optomix in series before the EXPO input on the STO to allow for
Dynamic FM (voltage control over the FM Index). Exponenital FM is much deeper and more complex then
Linear FM, however it will severely change the base frequency of the oscillator core and therefore the STO
will no longer track the 1V/ Octave scale properly. Exponential FM is highly useful when you require complex
signals but you do not require proper tracking, for example, if you are programming percussion sounds.
Oscillator SYNC
SYNC patches will introduce strong harmonics to all of the outputs on the STO. Sync uses a modulation
method where the core of the STO is made to conform to that of an external VCO. Once SYNC'd the STO
core will restart its period at each cycle of the external VCO signal, so they will have the same base frequen-
cy. Additional harmonics are achieved when the STO Frequency is HIGHER then that of the external VCO to
which it is SYNC'd. In a SYNC patch, the timbre of the STO may be altered by varying it’s frequency against
that of the Master Frequency as set by the external VCO signal. Slow sweeping modulation of the STO core
Frequency, such as an envelope or LFO patched to the EXPO IN, will result in sweeping of harmonics. The
best results are achieved by setting the external VCO to a base frequency of at least at least 100hz (around
A2) and sweeping the STO Frequency from 100hz up!
SYNC has the advantage of tracking much more reliably then Linear FM, however the sound is much more
aggressive.
Variable SHAPE
This circuit is unique to the STO. It gently ripples both Even and Odd harmonics, while always maintaining a
strong fundamental. At 0% the Variable SHAPE output is a SINE shape and at 100% it is a glitched triangle.
Although it is well capable of audio rate modulation, it is best served by slower modulations such as logarith-
mic envelopes and LFOs from MATHS and/ or FUNCTION and Smooth Random Voltages from the Woggle-
bug. When modulated and combined with the Sub-Oscillator (at the inputs of the MMG or Optomix) this
output will create a very strong voice for melodic sequencing.