How to Use the Logic Pro Vocoder: EVOC 20 PS

To use the Logic Pro vocoder, put EVOC 20 PS in the Instrument slot of a software instrument track, choose a vocal or other audio source from Analysis Input, and play or record MIDI notes on the EVOC track. The audio supplies articulation; the built-in synthesizer supplies pitch and harmonic material. You need both at the same time to hear the classic effect.

Verified September 4, 2026 against Apple's current EVOC 20 PS documentation. Current Logic labels the selector Analysis Input. Older tutorials may call it Side Chain, which is why the same setup appears under both search terms.

Understand the EVOC 20 PS signal flow

A vocoder compares two signals in frequency bands:

• Analysis signal: usually speech or singing. Its changing spectral shape carries consonants, vowels and rhythm.
• Synthesis signal: EVOC 20 PS's internal polyphonic synthesizer. MIDI notes determine its pitch and harmony.
• Vocoder output: the analysis envelopes reshape the synthesizer's filter bands.

Apple's EVOC 20 PS overview confirms that the instrument needs an Analysis Input from an audio track, live input or bus and incoming MIDI. The input doesn't “turn into MIDI.” It shapes the carrier you play.

Find the controls that matter first

Ignore most of the controls until the basic path makes sound. The shortest route is Analysis Input, MIDI notes and the Output Signal selector. Once that's working, use the analysis level, carrier brightness, filter bands and U/V section to improve speech.

Set up EVOC 20 PS with a recorded vocal

1. Create or choose a clean vocal audio track.
2. Create a new software instrument track.
3. Insert EVOC 20 PS in that track's Instrument slot.
4. In the plug-in header, choose the vocal track from Analysis Input.
5. Set the Output section's Signal menu to Voc.
6. Mute the dry vocal if you want to hear only the effect. Do not turn the track off, because the analysis signal must still reach EVOC.
7. Start playback, select the EVOC track and hold a MIDI chord.
8. Record or draw MIDI notes that follow the vocal phrasing.

If muting the vocal stops the vocoder in your routing, feed a bus to Analysis Input and control the audible dry channel separately. Routing should make the analysis signal available without forcing it into the mix.

Use a live microphone without feedback

1. Create an audio track with the microphone input and confirm a healthy level.
2. Keep speaker monitoring controlled; headphones are safer near an open mic.
3. Create the EVOC instrument track and choose the live input or mic track as Analysis Input.
4. Record-enable or monitor the source as required by the session.
5. Select the EVOC track and play MIDI while speaking or singing.
6. Record the MIDI performance and the clean microphone on separate tracks when future editing matters.

You don't need a special microphone. Clear articulation, low room spill and stable level matter more than a brand or transducer rule. Avoid clipping the analysis path, because distorted consonants get harder to shape later.

Build a carrier the voice can shape

Apple documents Dual and FM oscillator modes plus a noise generator. The right carrier depends on the role, but intelligible speech normally needs energy across the mid and high bands. A dark sine-like carrier can follow pitch while hiding consonants.

Start with:

• a bright digital waveform or modest FM tone;
• enough upper harmonics to carry consonants;
• short or moderate attack so syllables begin clearly;
• release long enough to connect the phrase without smearing the next word;
• simple chords before dense voicings.

Play the rhythm of the language. Holding one long chord under every phrase can work for a pad, but rhythmic MIDI often makes the words easier to follow and gives the effect a musical contour.

Prepare the analysis vocal for clarity

Apple's level and frequency tips say intelligibility improves when analysis level changes less and when speech has useful high-frequency content. That supports two measured moves:

• compress the analysis signal enough to keep quiet syllables present;
• use EQ to recover useful high-mid or treble articulation when the recording lacks it.

Don't crush every vocal or apply a fixed boost. Listen to sibilants, plosives and noise. Compression raises breaths and room tone too, and too much high-frequency boost can make U/V noise harsh. Edit bad noises before you ask the vocoder to interpret them.

Set the formant filter before chasing effects

Apple's formant filter guide describes paired analysis and synthesis banks with up to 20 filters. Low and High Frequency set the working range. Formant Shift moves the synthesis bands, Stretch changes their distribution, and Resonance emphasizes each band's center.

A practical order:

1. Use enough bands for the detail the part needs.
2. Set Low and High Frequency so the important voice range is not discarded.
3. Keep Shift and Stretch near neutral while judging intelligibility.
4. Raise Resonance only until diction or tone improves.
5. Move Shift or Stretch for a deliberate character after the words work.

High resonance combined with large formant moves can create piercing peaks. Lower monitor level before sweeping and use an analyzer only as support for the listening test.

Use U/V detection for consonants

Voiced sounds such as vowels have periodic pitch. Unvoiced sounds such as many s, f, t and sh components behave more like noise. Apple's U/V Detection guide explains that replacing unvoiced content can make speech less weak and more intelligible.

Increase the unvoiced contribution until consonants return, then stop before the result gets hissy. Judge it in the full mix. A setting that sounds exaggerated in solo can disappear behind cymbals, and one that sounds polished alone can be too soft to understand in context.

Use output modes as diagnostic tools

Apple's output guide defines three Signal choices:

• Voc: the vocoder result;
• Syn: the synthesizer carrier alone;
• Ana: the analysis input alone.

If Syn is silent, check MIDI, the selected EVOC track and its oscillator envelope. If Ana is silent, check Analysis Input, the source track and monitoring. When both work, return to Voc. Add Ensemble and Stereo Width only after you're sure the center stays clear and mono playback keeps the important phrase.

Record the performance and print it safely

Record MIDI on the EVOC track so harmony, rhythm, velocity and note length remain editable. Keep the clean vocal or source audio. Once the performance and sound are approved, route EVOC to an audio track or bounce it to create a named print.

Print from a consistent start point and include release tails. Keep the MIDI, source vocal and plug-in version in the project. The audio print protects the sound against future plug-in or system changes. The original parts keep everything editable.

Three vocoder roles that mix differently

Lead robotic vocal

Prioritize consonants, stable level and a centered image. Use fewer chord notes than you'd expect so the words don't blur. Layer a quiet dry vocal only when the effect needs human attack or pitch detail.

Vocoder harmony behind a lead

Program chord changes from the song harmony, shorten release around busy lyrics and filter lows that compete with bass. Pan or widen the support carefully while the dry lead anchors the center.

Rhythmic or non-vocal texture

Use drums, loops or found sound as Analysis Input. Intelligible words don't matter here, so larger formant movement, band modulation and wider output can become part of the rhythm. Keep transient level controlled to avoid sharp filter bursts.

Program MIDI that follows the phrase

The carrier performance decides whether the result speaks, sings or becomes a pad. Start by copying the lyric rhythm with note lengths. Place chord changes at harmonically meaningful words, and leave intentional gaps where the singer breathes. If a consonant disappears at the start of a note, don't drag the vocal out of time. Move the MIDI note slightly earlier, or shorten the carrier attack.

For a lead line, try one or two notes before a full chord. Fewer voices create a firmer center and make the syllable envelope easier to hear. For backing harmony, spread chord tones across a practical range and avoid very low notes that turn the carrier into indistinct rumble. Velocity may change the instrument response, so make loudness decisions by ear instead of assuming every note will speak equally.

Quantize only as tightly as the arrangement needs. The vocal has its own consonant timing, and a perfectly gridded MIDI chord can feel late against an early consonant or rushed against a laid-back phrase. Edit with the dry vocal and drums audible, then mute the dry guide to judge whether EVOC carries the intended rhythm by itself.

Mix the vocoder without losing the lyric

Set the EVOC channel level against the lead element before you add more effects. Remove low-frequency energy that duplicates bass or kick, but keep enough lower midrange for body. If the words are still vague, go back to analysis level, carrier brightness, band range and MIDI voicing. That's a better move than stacking exciters.

• Use a short room or delay when the center needs depth without a long wash.
• Send longer effects from the printed or stable EVOC output so tails remain predictable.
• Automate level phrase by phrase when consonants disappear behind drums.
• Keep low bands narrower than upper texture when the part competes with bass.
• Check the dry source is not leaking unintentionally through a parallel path.

Ensemble can thicken the carrier, while Stereo Width distributes filter-band output. Neither control fixes a weak analysis signal. Compare in mono after widening, because alternating bands across the stereo field can change the apparent diction when they're summed.

Automate character after the words work

Once the base phrase is intelligible, small automation moves can make the effect feel performed. Shift formants at the end of a line, open the synthesis filter into a chorus, shorten release before a rhythmic stop or widen a held note. Write one clear move at a time and return to the neutral phrase between experiments.

Don't put continuous motion on every parameter. The listener needs stable vowels and consonants to recognize language. Put the largest changes in gaps, sustained notes or repeated words, where the transformation supports the arrangement instead of fighting it.

EVOC 20 PS no-sound checklist

1. EVOC 20 PS is in an Instrument slot rather than used solely as an audio effect.
2. The correct audio track, input or bus is selected in Analysis Input.
3. The analysis source is playing or monitored.
4. The EVOC track is selected, record-enabled as needed, and receiving MIDI.
5. The MIDI notes overlap the spoken or sung audio.
6. Output Signal is set to Voc.
7. The EVOC level, channel fader and output routing are audible.
8. Ana and Syn monitoring confirm both halves of the path.

Common vocoder mistakes

• Expecting the vocal alone to create pitched output.
• Turning off the analysis track instead of separating its audible output.
• Using a carrier with too little high-frequency energy for clear speech.
• Holding dense chords that blur consonants and rhythm.
• Boosting resonance and formants before the routing and source are clean.
• Widening the effect until the center disappears in mono.
• Printing the effect without keeping source audio and MIDI.

Frequently asked questions

Where is the vocoder in Logic Pro?

Create a software instrument track and choose EVOC 20 PS in its Instrument slot. It is a vocoder instrument with a built-in synthesizer, not a simple insert on the vocal track.

Why does EVOC 20 PS need MIDI?

The analysis audio supplies articulation while MIDI plays the internal carrier's notes. Without overlapping MIDI, the vocoder has no pitched carrier to shape.

Is Analysis Input the same as the old Side Chain menu?

It serves the input-selection role shown as Side Chain in older tutorials. Follow the current Analysis Input label in the plug-in header.

Why can I hear the synth but not the vocoder?

Output may be set to Syn, or the Analysis Input is not receiving audio. Switch to Ana to verify the source, then return to Voc when both paths work.

How do I make EVOC 20 PS words clearer?

Stabilize the analysis level, preserve useful high-frequency speech content, choose a bright carrier, use enough bands, tune U/V detection and simplify the MIDI voicing.

How do I record the vocoder in Logic Pro?

Record MIDI on the EVOC instrument track while the analysis audio plays. When approved, route or bounce the EVOC output to audio and keep the original MIDI and source.

EVOC 20 PS final checklist

• Analysis Input receives a clean, intentional source.
• MIDI notes overlap every phrase that should sound.
• The carrier contains enough harmonic detail.
• Formant range and band count support the source.
• U/V detection restores consonants without harsh noise.
• Voc, Syn and Ana modes have been used to diagnose routing.
• The effect works in the mix and in mono.
• Source audio, MIDI and a named print are preserved.

Continue through the Logic Pro Create Music hub for MIDI, instruments, sampling and arrangement workflows.