10.6

140Logic Pro Effects
Freeze the input signal in EVOC 20 TrackOscillator
• In Logic Pro, click the Freeze button to hold, or sustain, the sound spectrum of the
analysis input signal.
By freezing the input signal you can capture a particular characteristic of the signal,
which is then imposed as a complex sustained filter shape on the Synthesis section.
Here are some examples of when this could be useful:
• If you are using a spoken word pattern as a source, the Freeze button could
capture the attack or tail phase of an individual word within the pattern—the
vowel a, for example.
• People cannot sustain sung notes indefinitely. To compensate for this human
limitation, use the Freeze button. If the synthesis signal needs to be sustained but
the analysis source signal—a vocal part—is not sustained, use the Freeze button
to lock the current formant levels of a sung note, even during gaps in the vocal
part, between words in a vocal phrase.
Tip: The Freeze parameter can be automated, which may be useful in this situation.
Set the number of filter bank bands in EVOC 20 TrackOscillator
• In Logic Pro, vertically drag the Bands field to set the number of frequency bands
the EVOC 20 TrackOscillator filter bank uses.
The greater the number of frequency bands, the more precisely the sound can be
reshaped. As the number of bands is reduced, the source signal frequency range is
divided up into fewer bands, and the resulting sound is formed with less precision by
the synthesis engine. A good compromise between sonic precision—allowing incoming
signals such as speech and vocals to remain intelligible—and resource usage is around
10 to 15 bands.
Tip: To attain the best possible pitch tracking, it is essential to use a mono signal
with no overlapping pitches. Ideally, the signal should be unprocessed and free of
background noises. Using a signal processed with even a slight amount of reverb, for
example, can produce unusual results. Processing a signal with no audible pitch, such
as drum loop, also delivers unusual results, but the resulting artifacts might be perfect
for your project.
Logic Pro EVOC 20 TrackOscillator U/V detection controls
Human speech consists of a series of voiced sounds—tonal sounds or formants—and
unvoiced sounds. The main distinction between voiced and unvoiced sounds is that voiced
sounds are produced by an oscillation of the vocal cords, whereas unvoiced sounds are
produced by blocking and restricting the air flow with lips, tongue, palate, throat,
and larynx.
If speech containing voiced and unvoiced sounds is used as a vocoder analysis signal but
the synthesis engine doesn’t differentiate between voiced and unvoiced sounds, the result
sounds rather weak. To avoid this problem, the synthesis section of the vocoder must
produce different sounds for the voiced and unvoiced parts of the signal.
EVOC 20 TrackOscillator includes an Unvoiced/Voiced detector. This unit detects
the unvoiced portions of the sound in the analysis signal and then substitutes the
corresponding portions in the synthesis signal with noise, with a mixture of noise and
synthesizer signal, or with the original signal. If the U/V Detector detects voiced parts,
it passes this information to the synthesis section, which uses the normal synthesis
signal for these portions.