NTCCRT: A concurrent constraint framework for soft-real time music interaction

Writing music interaction systems is not easy because their concurrent processes usually access shared resources in a non-deterministic order, often leading to unpredictable behavior. Using Pure Data (Pure Data) and Max/MSP, it is possible to program concurrency; however, it is difficult to synchronize processes based on multiple criteria. Process calculi such as the Non-deterministic Timed Concurrent Constraint (ntcc) calculus, overcome that problem by representing, declaratively, the synchronization of multiple criteria as constraints. In this article, we propose the framework Ntccrt, as a new alternative to manage concurrency in Pure Data and Max/MSP. Ntccrt is a real-time capable interpreter for ntcc. Using Ntccrt binary plugins in Pure Data, we executed models for machine improvisation and signal processing. We also analyzed two case studies: one of a machine improvisation system and one of a signal processing system. We found out that performance of both case studies is compatible with soft real-time music interaction; it means, a musician can interact with Ntccrt without noticeable delays during the interaction

Concurrent constraints models of music interaction

International audienceIn this chapter we follow this "economy of means" way to present several vari- eties of CCP calculi, starting from a very basic one and building from it by adding new features. A fundamental one for music applications is the ability to represent temporal behavior. This can be introduced within the context of determinate (tcc, utcc) or non-determinate (ntcc) computation. For the determinate case, we show how the addition of a process abstraction feature (utcc) allows to model dynamic musical structures in a very simple way. In particular, we model a dynamic version of interactive scores ([ALL 07]). For the nondeterminate case, we use the possibility of defining many alternative computational paths to model an agent following different rhythmic patterns constructed from a given basic one. We then go on to consider a more "metrical" notion of time (rtcc) based on uniform ticks used by processes to define their time of execution in a more fine-grained way, or to cause preemption of other processes at more precisely defined points in time. We use these new "real-time" features to describe a simple model of a basic form of musical dissonances