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Chapter 6 Filter 75
EVOC 20 TrackOscillator
The EVOC 20 TrackOscillator is a vocoder with a monophonic pitch tracking oscillator.
The tracking oscillator allows the EVOC 20 TrackOscillator to track (follow) the pitch of a
mono input signal. For example, if the input signal is a vocal melody, the individual
pitches of the sung notes will be tracked and mirrored by the synthesis engine.
The EVOC 20 TrackOscillator features two formant filter banks, an analysis and a
synthesis filter bank. Each has several (configurable) input parameters. You can use the
track into which the EVOC is inserted as the analysis signal source, or use another audio
track as the input source via a Side Chain. The synthesis source can be the track into
which the EVOC is inserted, another audio track, or the tracking oscillator. Each analysis
frequency band has an envelope follower that tracks the level of that band, so that it
can be remodeled more precisely.
The signal path of the EVOC 20 TrackOscillator is shown in the block diagram on page
168.
∏ Tip: For good pitch tracking, it is essential to use a mono signal (with no overlap of
pitches) that is as unprocessed as possible. Avoid using a signal with background
noises. Using a signal processed with even a slight amount of reverb, for example, will
produce strange (and likely undesirable) results. Even stranger results will result when a
signal with no audible pitch (such as drum loop) is used. In some situations, however,
the resulting artifacts might be desirable.
The EVOC 20 TrackOscillator is not limited to pitch tracking effects. It can vocode a
signal by itself, making it very useful for unusual filter effects. Try this with different
Resonance, Formant Shift, and Formant Stretch settings. As both analysis and synthesis
input signals are freely selectable, you can even vocode an orchestra with train noises,
for example.
More information about vocoders can be found in “Vocoder Basics” on page 150.