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EVOC 20 PolySynth performance tips
Level and frequency tips
A vocoder always generates the intersection point of the analysis and synthesis signals. If there’s
no treble portion in the analysis signal, the resulting vocoder output also lacks treble. This is also
the case when the synthesis signal has a lot of high-frequency content. Because this is true of
each frequency band, the vocoder demands a stable level in all frequency bands from both input
signals to obtain the best results.
Achieving a great “classic” vocoder effect requires both the analysis and synthesis signals to be
of excellent quality, and it also requires care to be taken with the vocoder parameters. These tips
will help you achieve the best possible results.
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The less the level changes, the better the intelligibility of the vocoder. You should therefore
compress the analysis signal in most cases.
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Due to the way human hearing works, the intelligibility of speech is highly dependent on
the presence of high-frequency content. To aid in keeping speech clear, consider using
equalization to boost or cut particular frequencies in analysis signals before you process them.
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If the analysis signal consists of vocals or speech, a simple shelving filter should be sufficient
to boost the high-mid and treble range, which is important for speech intelligibility.
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If the synthesis signal lacks treble energy, it can be generated with a distortion effect. The
Overdrive effect is perfect for this purpose.
Tips to avoid sonic artifacts
A common problem with vocoder sounds involves sudden signal interruptions—ripping,
breaking sounds—and rapidly triggered noises during speech pauses.
The Release parameter defines the time it takes for a given synthesis frequency band to
decrease in level if the signal level of the respective analysis band decreases abruptly. The
sound is smoother when band levels decrease slowly. To achieve this smoother character, use
higher Release values in the Analysis section. Take care to avoid setting an over-long release
time, because this can result in a less distinct, washy sound. Use short Attack values when a fast
reaction to incoming signals is required.
If the analysis signal is compressed as recommended, the level of breath, rumble, and
background noise will rise. These unwanted signals can cause the vocoder bands to open
unintentionally. To eliminate these artifacts, use a noise gate before using compression and
boosting the treble frequencies. If the analysis signal is gated appropriately, you may be able to
reduce the (Analysis) Release value.
Chapter 8 EVOC 20 PolySynth 153