OM-Chant is an OpenMusic library for the control of the Chant synthesizer. The Chant synthesiser was developed at IRCAM in the early 80s, in order to simulate and reproduce sung voice sounds, but also in order to create more abstract sounds using the same production model.

Chant is a reference implementation of the FOF synthesis technique (for French "Fonctions d'Ondes Formantiques", or formant wave functions), although it also embeds other signal generators or processing modules such as resonant filters or noise generators.

FOF synthesis allows to model the vocal production system considering an excitation signal and his response to a resonant system. In contrast with the more traditional "source-filter" model, the FOF synthesis generates trains of small signals (simple sinusoids multiplied by an exponential envelope) at a given frequency, which contribute to the overall spectrum of the resulting signal with a formant (typically, a FOF synthesiser is compound of several FOF generators in parallel, each one producing one formant).

Formants are modulations of the spectrum characterizing vocal signals. They can be described with few simple and intuitive parameters (central frequency, amplitude, bandwidth, etc.) which have a direct matching with the parameters of the FOFs.

Associated to the continuous / high-level control procedures provided in OM-Chant, FOF synthesis offers interesting possibilities challenging the limits of vocal synthesis.

This manual describes the functionalities of the OM-Chant library in version 2.0 (released, fall 2012).