pDM: An Expressive Sequencer with Real-Time Control of the KTH Music-Performance Rules

37 Experimental research in music performance is now an established field with a number of interesting advances relating to the understanding of the musical communication between performer and listener and Friberg forthcoming). From this research, it is evident that the performer has an important and essential role " giving life " to a composition by introducing gestural qualities, enhancing the musical structure, and providing a personal interpretation reflecting an expressive intention. For example, studies of emotional expression have shown that the same piece can communicate completely different emotions by changing the performance. A part of this research field has attempted to find and model the underlying performance principles used by the musicians (De Poli 2004; Widmer and Goebl 2004). One such system, the KTH rule system for music performance, is a result of a long-term research project initiated by Johan Sundberg The KTH rule system currently consists of about 30 rules covering different aspects of music performance. The input is a symbolic score, and the output is the expressive rendering in which the performance parameters such as " microtiming, " articulation, tempo, and sound level are shaped. The rules model typical performance principles such as phrasing, ar-ticulation, intonation, micro-level timing, rhythmic patterns, and tonal tension. High-level musical descriptions , such as emotional or motional expressions , can be modeled by using a selection of rules and rule parameters (Bresin and Friberg 2000). In the first development stage, rules were derived using the analysis-by-synthesis method: using the musician Lars Frydén as an expert judge, the computer was taught how to play more musically by implementing a tentative model, listen to the result, and then go back and make adjustments. Later real performance measurements were also employed later for modeling some of the rules. The project has resulted in about 60 publications, including three doctoral dissertations. (See www.speech.kth.se/ music/performance.) The program Director Musices represents the main implementation of the rule system. It was designed primarily for research purposes and is not suitable for real-time control. However, real-time control of the rule system has a number of potential applications. It could be used for interactive expressive control of the music in, for example, a conductor style, as is suggested below. Whereas previous conductor systems primarily controlled overall sound level and tempo (e.g., Mathews 1989; Borchers et al. 2004), this system would provide macro-level control of the overall expressive character by changing the musical …