Vocoder & speech

What happens inside

• Vowels are shaped by formants — peaks in their frequency spectrum, usually one to three of them. A “u” has peaks around 330 Hz and 1260 Hz, for example.
• The vocoder splits the incoming sound across a bank of tuned band-pass filters, like the filter’s band-pass mode but many at once.
• Each band has its own envelope follower, which turns that band’s loudness into a control voltage.
• Those voltages open matching filters on the carrier and recreate your loudness contour, band by band — formant peaks rise and fall separately as you speak.
• Resolution: the MicroFreak uses 16 bands. Classic vocoders had around ten and sounded mushier.

The Vocoder oscillator’s knobs

Wave

Picks the carrier. Fully anticlockwise it is a sawtooth; from about 11% it becomes a 50% pulse, which narrows as you turn until it reaches a 97% duty cycle at 90%. From 91% to fully clockwise it is noise.WAVE knob

Timbre

Sets the frequency range the analysis and resynthesis cover. A narrower range gives the vocoder fewer frequencies to watch, so it responds better; use it to suit a lower or higher voice, or the range of an instrument you use as the modulator.TIMBRE knob

Shape

Sets the bandwidth of each filter band. Higher settings make the bands narrower, which brings out the harmonics more.SHAPE knob

Getting the best from your voice

• The best carrier is a wave rich in overtones, which is why the Vocoder oscillator offers saw, pulse and noise.
• Articulate clearly — more than feels natural. Clear articulation opens up the filters.
• Plosives (p, t, b) and sibilants (s, ch, z) confuse the filter bank. A built-in high-pass filter removes them.
• A little artificial high end helps open the filters; that is what the hiss settings do (Vocoder settings and mic levels).

Fit the gooseneck microphone

1. 1Push the microphone unit into the headphone jack.
2. 2Line the black plastic gooseneck adapter up with the edges of the case and press gently but firmly to attach it.
3. 3To monitor, plug your headphones into the headphone output on the microphone base.

Or use a headset microphone

1. 1Plug the headset’s 3.5 mm TRRS jack into the MicroFreak’s headphone jack.

TRRS wiring (CTIA/AHJ standard)

In the Vocoder Edition box

• A white MicroFreak with a swan on the centre strip.
• The gooseneck microphone adapter and splitter: an electret microphone plus a headphone output that replaces the original one.
• A leaflet describing the microphone base and gooseneck.

Where the presets are

• The template presets start at slot 129 with the Square Poly template.
• The MicroFreak Vocoder Edition adds 16 vocoder presets in slots 304–320.
• When a vocoder preset is loaded, a small three-step level meter on the display reacts to your voice (Vocoder settings and mic levels).

Build your own from scratch

1. 1Load an Init preset.
2. 2Turn TYPE clockwise until the Vocoder type is selected.
3. 3Press SAVE to start saving (Saving presets), press PRESET, then turn it to choose the vocoder category.
4. 4Press PRESET again and give the preset a name if you like.
5. 5Press SAVE to store it.

While you play

• Turn WAVE, TIMBRE and SHAPE to change the carrier and the filter bank (How the vocoder works).
• Press PARAPHONIC and hold two or more keys to vocode chords (Paraphonic mode and chord mode).
• Try unison, and modulate its spread for a big moving sound (Unison).

Per-preset settings

Hiss modes

Off

Only the lower, “buzz” frequency range that vowels use.

Switched

A detector sorts your voice into voiced “buzz” sections (roughly vowels) and unvoiced “hiss” sections (roughly consonants). During hiss, white noise replaces the carrier oscillator. The output is gated: you only hear something while the modulator is detected, at a level that follows it.

Pass

You hear the vocoded synth plus everything in your voice above 5 kHz, so your voice bleeds through.

Global mic settings

Set the mic gain by ear

1. 1Set MASTER to about 50% and check the level with a few non-vocoder presets.
2. 2Select the Vocoder oscillator, press UTILITY and turn PRESET down to Mic Settings.
3. 3Press PRESET to open it, go to Mic Gain and press PRESET again to show the value.
4. 4Turn PRESET to the left, away from Auto Gain, to set a level yourself.
5. 5Hold a key and sing or speak; adjust until the output is loud enough but clean. Press PARAPHONIC to check with several notes too.
6. 6Watch the level meter: aim for the middle step and avoid the “skull”, which means distortion.

Mic detection

• With Mic Detection on, the MicroFreak checks for a microphone every time you load a vocoder preset or select the Vocoder oscillator.
• If none is found it shows warning! mic needed, disables the mic until the next preset is loaded and bypasses the filter bank — you hear only the raw Vocoder oscillator.
• Switch it off when you feed in an external source instead of a microphone.

Use an external source

1. 1Switch off the MicroFreak and gently remove the gooseneck microphone.
2. 2Turn the output level of your source all the way down to avoid clipping.
3. 3Plug the splitter into the MicroFreak’s headphone jack and the source into the splitter’s microphone branch.
4. 4Switch the MicroFreak on.
5. 5Set Utility > Mic Settings > Mic Detection to Off.
6. 6Set Mic Gain to -12 dB to start.
7. 7Select a vocoder preset, hold a key and slowly raise Mic Gain. If you still hear nothing, slowly raise the source’s level until the vocoder responds.

Wave: category

Timbre: formant

Shape: vowels

Shape: colours

Shape: numbers

Shape: letters and phonetics

Shape: synth terms