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Vocalization

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github-actions[bot] edited this page May 2, 2026 · 1 revision

Vocalization

Flow can synthesize singing and speech via formant synthesis and an optional text-to-speech hook. These live in @audio and produce ordinary Buffer values you can mix, effect, and export.

sing

Synthesize a vowel or consonant-vowel syllable at a given pitch and duration:

use "@std"
use "@audio"

Buffer vowel = (sing "ah" C4 0.5)
(play vowel)

Signature: (sing String syllable, Note pitch, Double seconds) -> Buffer

Vowels

The five core vowels are supported:

Syllable IPA Example
"ah" /a/ "father"
"ee" /i/ "see"
"eh" /e/ "bed"
"oh" /o/ "go"
"oo" /u/ "moon" 
use "@audio"

Buffer a  = (sing "ah" A4 0.3)
Buffer e  = (sing "ee" A4 0.3)
Buffer i  = (sing "eh" A4 0.3)
Buffer o  = (sing "oh" A4 0.3)
Buffer u  = (sing "oo" A4 0.3)

Buffer phrase = a -> appendBuffers e -> appendBuffers i -> appendBuffers o -> appendBuffers u
(exportWav phrase "vowels.wav")

Consonant-Vowel Syllables

Prefix a vowel with a supported consonant to get a syllable:

use "@audio"

Buffer na = (sing "na" C4 0.5)
Buffer ta = (sing "ta" E4 0.3)
Buffer sa = (sing "sa" G4 0.3)
Buffer la = (sing "la" C5 0.5)

The synthesizer applies a short consonant attack (plosive, fricative, or nasal) followed by the vowel formants.

Mixing Vocals with Instruments

Since sing returns a normal Buffer, you can mix and process it like any other source:

use "@std"
use "@audio"

Buffer vocal  = (sing "ah" C4 1.0)
Buffer tone   = (createSineTone 1.0 440.0 0.5)
Buffer mixed  = (mix vocal tone)

Buffer wet = mixed -> reverb 0.4 -> gain 0.0
(exportWav wet "vocal_mix.wav")

Different Pitches

Formant synthesis preserves vowel character across the usable vocal range:

use "@audio"

Buffer low  = (sing "oh" C3 0.5)
Buffer mid  = (sing "oh" C4 0.5)
Buffer high = (sing "oh" C5 0.5)

Very low or very high pitches may become less intelligible, as with real voices.

Text-to-Speech Hook

Flow can delegate a string to an external TTS engine (such as espeak-ng) and return the generated audio as a buffer.

Setting the TTS Command

use "@audio"

(setTtsCommand "espeak-ng -v en -w {out}")

The command template should write WAV output to the path substituted for {out}. The generated file is loaded back into a buffer and the temporary file is cleaned up.

Running TTS

use "@audio"

Buffer greeting = (tts "Hello from Flow")
(play greeting)

If no TTS command has been configured, or the engine is not installed, tts reports an error.

Exporting TTS Audio

Since the result is a standard buffer, it can be processed and exported:

use "@audio"

Buffer words = (tts "welcome to the piece")
Buffer wet   = words -> reverb 0.5 -> fadeOut 0.5
(exportWav wet "intro_voice.wav")

Use Cases

  • Singing synthesis: layer vocal buffers over instrumental parts to add a human timbre
  • Spoken intros/outros: use TTS for ambient narration or spoken-word pieces
  • Ear training / demos: name scale degrees or chords out loud inside longer renders
  • Phoneme play: sequence sing calls to build nonsense syllable patterns over a groove

Function Reference

Function Signature Description
sing (String, Note, Double) -> Buffer Formant-synthesized vowel or syllable
tts (String) -> Buffer External TTS → buffer (requires setTtsCommand)
setTtsCommand (String) -> Void Configure the TTS command template

See Also

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