Make Noise STO - FM, SYNC, and Variable SHAPE

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FM, SYNC, and Variable SHAPE:
The STO is capable of generating harmonically rich waveforms. This is accomplished through the modulation 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 Modulating 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 does not track accurately. Exponential FM
is also possible with the STO by patching your modulating oscillator to the 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 severely changes the base frequency of the oscillator core and
therefore the STO no longer tracks 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 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 restarts its period at each cycle of the external VCO
signal, so they will have the same base frequency. Additional harmonics are achieved when the STO Frequency is Higher than 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 Input, results 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 logarithmic envelopes and LFOs from MATHS and/or FUNCTION and
Smooth Random Voltages from the WOGGLEBUG. When modulated and combined with the Sub-Oscillator (at the inputs of the
MMG or Optomix) this output creates a very strong voice for melodic sequencing.