Artificially intelligent accompaniment using Hidden Markov Models to model musical structure
2008. Co-authored with Alan Smaill. In Proceedings of the Fourth Conference on Interdisciplinary Musicology (CIM’08), Thessaloniki, Greece
For performing musicians, musical accompanists may not always be available during practice, or an available... more
For performing musicians, musical accompanists may not always be available during practice, or an available accompanist may not have the technical ability necessary. As a solution to this problem, many musicians practise with pre-recorded accompaniment. Such an accompaniment is fixed and does not interact with the musician’s playing: the musician must adapt their performance to match the recording. To synchronise accompaniment with the soloist, it is preferable that an accompanist should be able to follow the musician through the score as they play, rather than the other way around. During performance, musicians may deviate from what is written in the score (either intentionally, by adding their own musical interpretation, or accidentally, by making performance errors). The accompanist should adjust their playing to follow the soloist.
This work investigates how an artificial musician can follow a human musician through the performance of a piece (perform score following) using a Hidden Markov Model of the piece’s musical structure. The computer musician is designed to interact with the human musician and provide accompaniment as a human accompanist would: musically and in real time. Having successfully implemented this representation, the performances of the resulting artificial accompanists has been evaluated both qualitatively, by human testers and quantitatively, by objective criteria based on that used at the Music Infomation Retrieval and EXchange Conference in 2006. The artificial accompanists can, in general, accompany human performers with a reasonable degree of accuracy. Testing has also raised an interesting reflection on the nature of co-operation between soloist and accompanist, and more generally on the role of the computer musician in ensemble performance.
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Seen by:Investigating the role of score following in automatic musical accompaniment
2009. Co-authored with Alan Smaill. Journal of New Music Research Vol. 38 No. 2 pp. 197-209
When suitable accompanists are not available to a soloist
musician, an alternative possibility is to use... more
When suitable accompanists are not available to a soloist
musician, an alternative possibility is to use computer-generated accompaniment. A computer accompanist should interact with the soloist and adapt to the soloist’s playing as a human accompanist would, both reacting to expressive nuances of tempo and to unintentional errors such as wrong or mistimed notes. Over the past 25 years, accompaniment systems have been developed, all of which employ some form of score following: the process of following a musician’s progress through the score of a piece during performance. This work considers the role of score following in automatic accompaniment. In this
investigation we developed a computer accompanist that employs score following. Our computer musician uses Hidden Markov Models to model the score by metrical structure and to provide accompaniment to a soloist playing monophonic music in real time, as the soloist is playing. Working with MIDI input/output, it tracks tempo fluctuations, anticipates the soloist’s next note and supports some amount of unintentional deviation from the score. Qualitative evaluation, by human testers, and quantitative evaluation, using measurable criteria taken from MIREX, reported that the system performs adequately. We then used interviews with eight human accompanists to consider how well a score following system models the accompaniment process. This evaluation raises questions about the musical interaction between soloist and accompanist that have received relatively little attention. The information we gathered from interviews suggests the importance of other aspects of accompaniment, such as the sharing of shape of the performance between musicians, rather than treating the accompanist as purely subservient. We discuss the implications of these issues for the design of automated accompanists.
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