- Artificial Evolution of Expressive Performance of Music:An Imitative Multi-Agent Systems Approach
As early as the 1950s and early 1960s, pioneers such as Lejaren Hiller, Gottfried Michael Koenig, Iannis Xenakis, and Pietro Grossi, among a few others, started to gain access to computers to make music. It soon became clear that to render music with a so-called "human feel," computers needed to process information about performance (e.g., deviations in tempo and loudness), in addition to the symbols that are normally found in a traditional musical score (e.g., pitch and rhythm). This was especially relevant for those interested in using the computer to play back scores.
Indeed, the first ever attempt at creating a computer-music programming language, by Max Mathews at Bell Telephone Laboratories in 1957, was motivated by his wish to "write a program to perform music on the computer" (Park 2009 p. 10). It appears that this development began after Mathews and John Pierce went to a piano concert together. During the intermission, Pierce suggested that perhaps a computer could perform as well as the pianist. Mathews took up the challenge, which resulted in Music I, the ancestor of music programming languages such as Csound (Boulanger 2000).
Research into computational models of expressive performance of music (Widmer and Goebl 2004) is still an active area of study—particularly, research into devising increasingly more sophisticated automated and semi-automated computer systems for expressive music performance, hereinafter referred to as CSEMP.
A CSEMP is able to generate expressive performances of music. For example, software for music typesetting is often used to write a piece of music, but most packages play back the music in a "robotic" way, without expressive performance. The provision of a CSEMP engine would enable such systems to produce more realistic playback.
A variety of techniques have been used to implement CSEMPs (Widmer and Goebl 2004; Kirke and Miranda 2009; in press). These include (1) rule and grammar-based approaches (Sundberg, Askenfelt, and Frydén 1983; Clynes 1986; Bresin and Friberg 2000; Livingstone et al. 2007), including expert systems (Johnson 1991); (2) linear and nonlinear regression systems (Canazza et al. 2000; Ishikawa et al. 2000), including artificial neural networks (Bresin and Vecchio 1995; Camurri, Dillon, and Saron 2000), Hidden Markov Models (Grindlay 2005), Bayesian Belief Networks (Raphael 2001), Sequential Covering methods (Widmer and Tobudic 2003), and Regression Trees (Ramirez and Hazan 2005); and (3) evolutionary computing methods (Zhang and Miranda 2006; Ramirez et al. 2008). In this article, we introduce a new approach using the imitative multi-agents paradigm.
Expressive Music Performance
How do humans make their performances sound so different from the so-called "robotic" performance a machine would normally give? In this article, the strategies and changes that are not marked in a score but which performers apply to the music are referred to as expressive performance actions. Two of the most common expressive performance actions in Western classical music are changing the tempo and the loudness of the piece as it is played. These are tempo and loudness changes not marked on the score; they are additional to notated tempo or loudness changes, such as accelerando or mezzo-forte. For example, a common expressive performance strategy is for the performer to slow down as they approach the end of the piece (Friberg and Sundberg 1999). [End Page 80] Another expressive performance action is the use of expressive articulation—for instance, when a performer chooses to play notes in a more staccato (short and pronounced) or legato (smooth) way. Those who play instruments with continuous tuning, for example string players, can also use expressive intonation, making notes slightly sharper or flatter, and such instruments also allow for expressive vibrato. Many instruments provide the ability to expressively change timbre as well.
There have been a number of studies intoWestern pre-20th-century classical music performance, notably involving the music of the Baroque, Classical, and Romantic periods. On of the earliest systematic studies was developed in the late 1930s (Seashore 1938), and more recently good reviews have been published (e.g., Palmer 1997; Gabrielsson 2003). One element of these studies has been to discover what...