Copyright © Freund Publishing House Limited Int J Dis Human Dev 2006;5(2):00-00 _______________________________________________________________________________________________________________ 00 Brain-Computer music interface for composition and performance Eduardo Reck Miranda, MSc, PhD University of Plymouth, Interdisciplinary Centre for Computer Music Research (ICCMR), Drake Circus, Plymouth, United Kingdom Abstract: This paper introduces a new brain-computer interface (BCI) system that uses electroencephalogram (EEG) information to steer generative rules to compose and perform music. It starts by noting the various attempts at the design of BCI systems, including systems for music. Then it presents a short technical introduction to EEG sensing and analysis. Next, it introduces the generative music component of the system, which employs our own adapted version of a machine-learning technique based on ATNs (Augmented Transition Networks) for the computer-replication of musical styles. The system constantly monitors the EEG of the subject and activates generative rules associated with the activity of different frequency bands of the spectrum of the EEG signal. The system also measures the complexity of the EEG signal to modulate the tempo (beat) and dynamics (loudness) of the performance. Subjects can be trained to select between different classes of generative rules to produce original pieces of music. Keywords: assistive music technology, brain-computer interface, generative music systems, bio-signal music controller, United Kingdom Correspondence: Eduardo Reck Miranda, MSc, PhD, Professor of Computer Music, University of Plymouth, SoCCE, B326 Portland Square, Drake Circus, Plymouth PL4 8AA, United Kingdom. E-mail: eduardo.miranda@plymouth.ac.uk Submitted: February 02, 2006. Revised: March 01, 2006. Accepted: March 05, 2006. INTRODUCTION Research into brain-computer interface (BCI) for music is an interesting arena for the development of new possibilities in recreational and therapeutic devices for people with physical and neurological disabilities. We shall refer to such systems as brain-computer music interfaces (BCMI). Various music-making devices are available for those with disabilities, and even though such devices have proved to work very effectively, they often do not allow as much control for those with severe physical disabilities. At present, access music tutors and therapists use gesture devices and adapted accessible technology to make this possible, which achieve excellent results. Yet, for people with severe physical disabilities, having complete control of the environment created for them by the facilitator or therapist can sometimes be difficult. This paper introduces a BCMI that uses the EEG to steer generative musical rules to compose and perform music on a MIDI-controlled mechanical acoustic piano (Figure 1). Human brainwaves were first measured in 1924 by Hans Berger, who termed these measured brain electrical signals the electroencephalogram, literally "brain electricity writing" (1). Today, the EEG has become one of the most useful tools in the diagnosis of epilepsy and other neurological disorders. Further, the fact that a machine can read signals from the brain has sparked the imaginations of scientists, artists and other enthusiasts, and EEG has made its way into applications other than strictly clinical ones. In the early 1970s, Jacques Vidal did the first tentative work towards a brain-computer interface (BCI) system. The results of this work were published in 1973 (2). Despite a number of isolated initiatives at building BCI systems, research in this area did not take off until the early 1990s, probably due to technological limitations. In 1990, Jonathan Wolpaw and colleagues developed a system to allow some control of a computer cursor by individuals with severe motor deficits. Users were trained to use aspects of their EEG to move a cursor on a computer screen (3). In 1998, Christoph Guger and Gert Pfurtscheller reported impressive advances in BCI research: an EEG-based system to control a prosthetic hand (4). Many attempts followed Fig. 1: The BCMI system in action. Note the keys of the piano being played by the system; no hands or any kind of physical movement are needed.