EVOC 20 PS analysis controls in Logic Pro

The parameters in the Sidechain Analysis section control how EVOC 20 PS analyzes and uses the input signal. Be precise with these parameters to attain the best possible speech intelligibility and the most accurate tracking.

Sidechain analysis parameters

Attack knob: Determine how quickly each envelope follower—coupled to each analysis filter band—reacts to rising signal levels. Longer attack times result in a slower tracking response to transients—level spikes—of the analysis input signal. A long attack time on percussive input signals—a spoken word or hi-hat part, for example—will translate into a less articulated vocoder effect. Set the Attack parameter to the lowest possible value to enhance articulation.
Release knob: Determine how quickly each envelope follower—coupled to each analysis filter band—reacts to falling signal levels. Longer release times cause the analysis input signal transients to sustain for a longer period at the vocoder output. A long release time on percussive input signals—a spoken word or hi-hat part, for example—will translate into a less articulated vocoder effect. Use of extremely short release times results in rough, grainy vocoder sounds. Release values of around 8 to 10 milliseconds are useful starting points.
Freeze button: Turn on to hold, or freeze, the current analysis sound spectrum indefinitely. When Freeze is enabled, the analysis filter bank ignores the input source, and the Attack and Release knobs have no effect.
Bands field: Drag to set the number of frequency bands (up to 20) used by the filter banks.

Freeze the input signal

Freezing the input signal lets you 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. The Freeze parameter can be automated, which may be useful in this situation.

In Logic Pro, click the Freeze button to hold, or sustain, the sound spectrum of the analysis input signal.

Set the number of filter bank bands

In Logic Pro, drag vertically on the Bands field to set the number of frequency bands used by the EVOC 20 PS filter bank.
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. You may find that 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.

Download the guides:

Logic Pro User Guide: Apple Books | PDF

Logic Pro Instruments: Apple Books | PDF

Logic Pro Effects: Apple Books | PDF

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