Expression marks for programming interactive music

The present work uses common Western music notation to represent logical and systematic behaviours of computer music processes in the context of score-oriented interactive music. The algorithmic representation is described by adding programming annotations in a controlled natural language to a musical staff as expression marks in the score. We implemented a computational environment that is able to translate these expression marks into coding instructions and execute them in real-time during a live performance of an interactive-music piece. A collection of short interactive music exercises for MIDI-controlled piano based on the proposed notation was composed and edited using music engraving software. During the compilation stage, an encoded version of the score in MusicXML format is translated into scripting code, and during live performance the computational environment executes the code in real time in sync with the human-performed parts. This paper introduces the syntax of expression marks for programming interactive music through a classic "Hello World" example in the context of interactive music and explains the technical details behind the implementation of the computational environment. The main motivation behind this work was to evaluate the viability of creating a cohesive symbolic representation of interactive music that is independent of specific software and hardware frameworks, and is strongly connected with the western music tradition.