technologies

esearch and development – 2016
orchestration assistance
—
Teams Involved: Musical Representations, Sound Analysis & Synthesis
The Orchestration project is an integral part of Sample
Orchestrator. It hopes to provide composers with a tool
to assist orchestration that is integrated in the software
environments created at IRCAM to assist composition,
such as OpenMusic. By taking advantage of the knowledge
acquired through large databases of instrumental sounds—
taking into account the breadth of the possibilities of
musical instruments—and the progress in the understanding
of pitch, we hope to help composers explore the array of
sound possibilities available with an orchestra. The problem
consists of finding the combinations of instrumental sounds
that are the closest to a target defined either from a recorded
sound or from a more abstract process (overlapping pitches,
for example) via a search by similarity defined by the user.
The major scientific issues lie, from a signal analysis point of
view, in the choice of a group of ‘characteristics’ that can be
calculated from samples of instrumental sounds, pertinent
in terms of their timbre description, and that make it possible
to predict—without having to listen or to analyze—the timbre
of an overlapping of sounds. The chosen approach consists
of incorporating the knowledge gained from the analysis of
large sound databases and a set of “instrument models”,
making it possible to estimate the probability that a certain
sound will be played by an instrument or by a group of
instruments. For the time being, this is limited to static
harmonic sounds and to periodic temporal vibrations (such
as a tremolo or a vibrato) but in time the application will
be improved to the point where will work for all types of
sounds.
Another issue concerns the management of the
combinatorial analysis adapted to the manipulated data,
the complexity of the problem makes it impossible to assess
the range of possible solutions. The method currently being
explored through an interactive environment lets us offer a
group of solutions to a composer, in a reasonable time frame,
where certain zones of research could be favored over
others that are less likely to lead to interesting solutions.
The search for an orchestration therefore becomes an
iterative process, during with pertinent solutions and user
preferences surface simultaneously. Technically speaking,
the interesting solutions are close to a multi-criteria Pareto
distribution optimization problem.
56