Section: New Results

Operational Timed Semantics

Participants : José Echeveste, Jean-Louis Giavitto, Florent Jacquemard, Arshia Cont.

One common use-case of real-time musical interactions between musicians and computers is Automatic Accompaniment where the system is comprised of a real-time machine listening system that in reaction to recognition of events in a score from a human performer, launches necessary actions for the accompaniment section. While the real-time detection of score events out of live musicians' performance has been widely addressed in the literature, score accompaniment (or the reactive part of the process) has been rarely discussed. In [13] , we are trying to deal with this missing component in the literature from a programming language perspective. We show how language considerations would enable better authoring of time and interaction during programming/composing and how it addresses critical aspects of a musical performance (such as errors) in real-time. We sketch the real-time features required by automatic musical accompaniment seen as a reactive system and formalize the timing strategies for musical events taking into account the various temporal scales used in music. Various strategies for the handling of synchronization constraints and the handling of errors are presented.

The behavior of the system Antescofo have been formally modeled as a network of parametric timed automata. The model obtained provides operational semantics for the input scores, in particular the interaction between the instrumental and electronic parts and the timing and error handling strategies mentioned below. This approach enables better authoring of time and interaction during programing/composing, permitting to use state of the art software verification tools for the static analysis of Antescofo scores. It also provides means to address critical aspects of musical performances in real-time.