Formant synthesis voice based on the IRCAM CHANT project (Rodet, Potard, Barriere, 1984).
Intone generates vocal-character sound using 5 parallel formant cells, each producing overlapping FOF (Formant Wave Function) grains: damped sinusoids at formant frequencies. A vowel morph slider smoothly interpolates through /a/, /e/, /i/, /o/, /u/ presets.
16 HP. Monophonic audio output.
How formant synthesis works
The human voice’s distinctive character comes from resonances (formants) in the vocal tract. Different vowel sounds correspond to different formant frequency patterns. Intone models this by summing 5 parallel resonant cells, each generating sound at a formant frequency.
Each formant cell generates FOF grains: short bursts of a damped sinusoid at the formant’s center frequency, with a cosine-windowed attack and exponential decay. Multiple FOFs overlap as they’re re-triggered at the fundamental frequency rate, creating a continuous tone with formant resonance character.
Three excitation modes
Default (nothing patched): Internal F0 oscillator drives FOF generation. V/Oct controls pitch. Works as a vocal-character VCO.
Audio mode (audio patched, switch up): Input audio passes through a parallel resonant bandpass filter bank at the 5 formant frequencies. The audio is formant-shaped: drums gain vocal coloring, oscillators acquire vowel character. V/Oct transposes the formant pattern.
Trigger mode (clock patched, switch down): External rising edges fire fresh FOF grains. Each trigger produces a vowel-character burst. V/Oct transposes the formant frequencies.
Controls
Per-Formant (x5)
| Control | Range | Default | Function |
|---|---|---|---|
| Freq offset | ±1 octave | 0 | Shifts formant frequency relative to vowel preset |
| Bandwidth | 30-500 Hz | 80 Hz | Width of the formant resonance |
| Amplitude | 0-1 | varies per formant | Level of this formant |
Global
| Control | Range | Default | Function |
|---|---|---|---|
| Vowel Morph (slider) | 0-1 | 0 (/a/) | Sweeps through /a/ → /e/ → /i/ → /o/ → /u/ |
| Skirt | 0-1 | 0.5 | FOF attack rate / spectral slope |
| Mode Switch | Audio/Trigger | Audio | Selects excitation mode when EXC is patched |
Inputs
| Input | Range | Function |
|---|---|---|
| V/Oct | 1V/octave | Pitch (default) or formant transposition (audio/trigger) |
| EXC | ±5V | Excitation source |
| F1-F5 Freq CV | ±5V | Per-formant frequency modulation |
| F1-F5 BW CV | ±5V | Per-formant bandwidth modulation |
| Vowel CV | 0-10V | Vowel morph position |
| Skirt CV | ±5V | Skirt width modulation |
Outputs
| Output | Function |
|---|---|
| Out | Monophonic audio output |
Vowel preset frequencies (Hz)
| Vowel | F1 | F2 | F3 | F4 | F5 |
|---|---|---|---|---|---|
| /a/ | 730 | 1090 | 2440 | 3400 | 4400 |
| /e/ | 530 | 1840 | 2480 | 3400 | 4400 |
| /i/ | 270 | 2290 | 3010 | 3400 | 4400 |
| /o/ | 570 | 840 | 2410 | 3400 | 4400 |
| /u/ | 300 | 870 | 2240 | 3400 | 4400 |
Spectrum display
Shows 5 formant peaks as colored bell curves on a logarithmic frequency axis (50 Hz - 5 kHz), with a bright composite envelope overlay. Updates in real time as parameters change.
Patch ideas
Vowel Pad: Patch a slow LFO to Vowel CV. The oscillator morphs between vowel sounds continuously.
Vocal Filter: Patch audio to EXC (Audio mode). Drum loops, oscillators, or samples get formant-shaped through the 5 vowel resonances.
Triggered Vowels: Patch a clock to EXC (Trigger mode). Each pulse produces a short vocal burst. Modulate Vowel CV for changing articulation.
Formant Sweep: Patch an LFO to one of the F1-F5 Freq CV inputs. The formant peak sweeps independently of the vowel preset.
Historical context
Based on the FOF technique from the IRCAM CHANT project (1979-1984), originally developed for singing voice synthesis. The same technique was used by composers including Kaija Saariaho, Gerard Grisey, and Marco Stroppa for spectral music composition.