# Aspects temporels d'un système de partitions musicales interactives pour la composition et l'exécution

Abstract : At a time when electro-acoustic music involves more and more signal processing during the composition process, the question of the musical interpretation of such pieces still remains open. Often, these pieces mainly consist in the recording, on a medium, of an in-time organization of "out of time'' musical materials. During a performance, the piece is broadcasted while the performer may only modify some global parameters such as the volume, the balance or the spatialisation. But he cannot "interpret" the piece in the same sense that a performer interprets a classical score. We would like to be able to perform this kind of works within a "musical interpretation" framework. This involves some kind of "interactive score", whose execution may adapt to the environment (e.g. other performers or control interfaces). In such situtation, the score is performed by the machine, leading to a different problematics than the one adressed by score following algorithms. We aim at creating a system that comprises of : an environment of assisted composition allowing the composers to design interactive scores ; and an execution machine controlled by performers in order to interpret such scores. We assume that this environment needs a formal representation of interpretable'' music. We base our work on a formalization of the interpretation in instrumental music, and try to generalize it to pieces of music that involve generic processes in place of the notes''. We limit our study to a particular side of the musical interpretation called the agogic modifications'', which means the possibility for the performer to interactively modify the occurrence time of some discrete events of the score during the performance. It is important to note that these events are associated with control points (beginnings, ends, or pivot points) of temporal processes, so by controlling these points in time, one may change the temporal deployment of music material. But these possibilities of "interpretation" are bounded by the composer at the time when the score is composed (just as in instrumental music). Such constraints imposed by the composer may express a compositional strategy. They are also useful for preventing from a disorganization of the piece during the performance. We propose such a formal description of interactive scores, by using a 2D block representation as one can find in the Maquettes'' of the OpenMusic software or the PD Data Structures . A score is constituted by a set of objects organized over a time-line. These objects are defined as sequences of discrete control points (a beginning, an end and intermediate pivot points). The objects denote the execution of processes that bear the musical content (whether it be signal or event processing or even complex logical computing). To define the limits of the interpretation frame, the composer can specify temporal constraints between the control points of the score : qualitative precedence constraints used to impose a partial order among the control points ; quantitative constraints used to specify ranges of possible values for the time intervals between control points. The score is thus both completely defined, and flexible in its internal temporal structure, which leaves room to interpretation. In addition the composer may set chosen control points in the score to be" interactive" i.e. linked to external events that are supposed to occur during the performance. These events may consist of control action on an interface or may result from the detection of something happening in the musical context. When a score is executed, the execution machine tells the processes when the execution time matches the logical time of a control point. This may happen for non-interactive control points just because time has passed, or, in the case of interactive points , because the associated external event has just occurred. Simultaneously, the execution machine checks for possible violations of the temporal constraints built into the score. In the case of a violation, the execution machine may change the future mapping between logical time and execution time in order to maintain score consistency. This may change the expected execution time for future points, and this may change the ordering as well. A constraint propagator is used for that purpose. Consistence checking may lead the machine to ignore external events in the case when they break the constraint system, or the machine can also "simulate" the occurrence of an external event that is awaited for too long and, for that reason, generates a violation in the constraint system. In addition to the interactive score formalism, we present an abstract machine for the execution that uses an internal representation of the score execution dynamics based on a Petri net associated to a constraints propagation algorithm. We also present an algorithm for compiling the interactive scores from the formal description to the representation used by the execution machine. We have developed a prototype mainly in OpenMusic that comprises : an extension of the OM maquettes for interactive score edition with an XML exchange format and a design constraints propagator; a compiler ; an execution machine that communicates with PureData through UDP. We present some applications, from the composition and interpretation of electro-acoustic scores to the interpretation of instrumental scores by technically limited musicians or impaired persons.
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https://tel.archives-ouvertes.fr/tel-00516350
Contributor : Antoine Allombert <>
Submitted on : Thursday, September 9, 2010 - 12:22:56 PM
Last modification on : Wednesday, May 15, 2019 - 3:40:04 AM
Long-term archiving on : Friday, December 10, 2010 - 2:51:54 AM

### Identifiers

• HAL Id : tel-00516350, version 1

### Citation

Antoine Allombert. Aspects temporels d'un système de partitions musicales interactives pour la composition et l'exécution. Autre [cs.OH]. Université Bordeaux 1, 2009. Français. ⟨tel-00516350⟩

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