# Vocoder

Commands ▸ Effects ▸ Vocoder… in the sample editor imposes the spectrum of
one sound on another and puts the result in an instrument slot. It is a port
of Emanuel Borsboom's Zerius Vocoder 1.3. Unlike the other effect windows it
does not process the sample in front of you: both sounds are picked from the
module.

## Carrier

The sound that is **played**: its spectrum is what you hear. It is looped for
as long as the modulator needs, so something rich and sustained works best —
noise, a string chord, a saw. A stereo carrier gives a stereo result.

Both lists offer every sample slot, then every sound in the project that no
slot plays. A slot with a slice gives its slice. A packed (ADPCM) sample is
listed but greyed, because it cannot be read. Hover a sound for its length,
channels and rate.

## Pitch, under Carrier

Plays the carrier at this note. The carrier is resampled onto the render's
rate, so this is the note the vocoder sings; **as recorded** leaves it at its
own default pitch. The line beside it gives the rate, length and channels at
that note.

## Modulator

The sound whose spectrum **shapes** the carrier — speech, usually. It is
mixed to mono, and its length is the length of the result. It starts on a
different sound from the carrier.

## Pitch, under Modulator

Plays the modulator at this note. Nothing is resampled: the whole render runs
at that rate, so speech gets faster and higher together, and with **Tuning**
at *as processed* the result moves with it.

## Bands

How many frequency bands the modulator is split into, 4 to 128. More bands
make the result sound more like the modulator; 8 to 64 is the usual range.
There can be at most half as many bands as the window has samples, and the
slider stops there.

## Window and Overlap

**Window** is how many samples are analysed at a time. Too long and the words
blur; too short and the pitch does. **from the rate** takes the largest power
of two up to a fifteenth of a second at the render's rate — the original's
own rule of thumb — between 64 and 8192.

**Overlap** is how far consecutive windows cross-fade: half the window (the
default, and usually the best of the three), a quarter or an eighth. The line
under the row gives the window in samples and milliseconds, and the overlap.

## Volume and Normalise

**Volume** scales the output, 0 to 4. The vocoder clamps at full scale, so
raising it trades headroom for level.

**Normalise** is on by default, as in the original: each band's gain is
divided by the carrier's own energy in that band, so a carrier with an uneven
spectrum does not colour the result. Off is the original's `-N` switch: the
modulator's magnitudes are used as they are.

## Preview

**Preview** renders in the background, with a progress bar and a **Cancel**.
Cancel stops at once when the page is cross-origin isolated; otherwise it
stops between channels, and the line under the bar says so. **Audition** plays
the preview, and **UNDO PREVIEW** and **REDO PREVIEW** step back and forth
through earlier ones. Changing any setting above the waveform drops the
preview, and says so.

## Output

**New instrument slot (N)** is the default: the first empty slot, or a new
one on the end. The number is the slot it will be; a module holds at most 63.
**Overwrite instrument N** replaces the instrument the sample editor is on,
and asks first.

## Name, Depth and Tuning

**Name** takes up to 40 characters; left blank it is *VOC* followed by the
modulator's and the carrier's names. **Depth** is what the slot stores, 16 or 8-bit; the result
is kept at full precision alongside it either way.

**Tuning** is the note that plays the result at its natural speed — the
instrument's default pitch. It changes no audio. **as processed** keeps the
render's own rate, to a thousandth of a hertz, so the default pitch is the
nearest note with a finetune that makes it exact. The line under it gives the
rate and the note it lands on.

The line below that says how long the result will be — the modulator's own
length, or its slice — and whether it is stereo (from a stereo carrier) or
mono.

## Apply

Writes the preview into the slot, rendering one first if there is none.
Loading into an existing slot is one step of undo; adding a slot and loading
it are two.