10.6

137Logic Pro Effects
EVOC 20 TrackOscillator
Logic Pro EVOC 20 TrackOscillator overview
EVOC 20 TrackOscillator is a vocoder with a monophonic pitch tracking oscillator. The
tracking oscillator tracks, or follows, the pitch of a monophonic input signal. If the input
signal is a sung vocal melody, the individual note pitches are tracked and mirrored, or
played, by the synthesis engine.
EVOC 20 TrackOscillator features two formant filter banks, an analysis bank, and a
synthesis filter bank. Each offers multiple input options.
You can capture an analysis signal source by using the audio arriving at the input of the
channel strip that EVOC 20 TrackOscillator is inserted into or by using a side chained
signal from another channel strip.
The synthesis source can be derived from the audio input of the channel strip that
EVOC 20 TrackOscillator is inserted into, a side chain signal, or the tracking oscillator.
Because you can select both the analysis and synthesis input signals, EVOC 20
TrackOscillator is not limited to pitch tracking effects; you can also use it for unusual
filter effects. For example, you could filter an orchestral recording on one channel strip
with train noises side chained from another channel strip. Or you could use it to process
drum loops with side chained signals, such as other drum loops or rhythmic guitar, clavinet,
and piano parts.
Vocoder overview
The word vocoder is an abbreviation for voice encoder. A vocoder analyzes and transfers
the sonic character of the audio signal arriving at its analysis input to the synthesizer
sound generators. The result of this process is heard at the output of the vocoder.
The classic vocoder sound uses speech as the analysis signal and a synthesizer sound as
the synthesis signal. This sound was popularized in the late 1970s and early 1980s. You
may be familiar with tracks such as “O Superman” by Laurie Anderson, “Funkytown” by
Lipps Inc., and numerous Kraftwerk pieces—such as “Autobahn,” “Europe Endless,”
“The Robots,” and “Computer World.”
In addition to these “singing robot” sounds, vocoding has also been used in many films—
such as with the Cylons in Battlestar Galactica, and most famously, with the voice of
Darth Vader from the
Star Wars saga.
Vocoding, as a process, is not strictly limited to vocal performances. You could use a drum
loop as the analysis signal to shape a string ensemble sound arriving at the synthesis input.
The speech analyzer and synthesizer features of a vocoder are two bandpass filter banks.
Bandpass filters allow a frequency band—a slice in the overall frequency spectrum—to
pass through unchanged. Frequencies that fall outside the band are cut.
In the EVOC 20 plug-ins, these filter banks are named the analysis and synthesis banks.
Each filter bank has a matching number of corresponding bands—if the analysis filter bank
has five bands (1, 2, 3, 4, and 5), there is a corresponding set of five bands in the synthesis
filter bank. Band 1 in the analysis bank is matched to band 1 in the synthesis bank, band 2
to band 2, and so on.