Page  00000043 Pocket Gamelan: mobile media for microtonal performance Greg Schiemer and Mark Havryliv Sonic Arts Research Network, University of Wollongong, Abstract We will demonstrate new live performance scenarios for performing microtonal music using bluetooth-enabled mobile phones and new tools designed for live performance realization. Interaction between mobile phones via wireless link is a key feature of the performance interface. Both scenarios are discussed in the context ofpublicly performed works for an ensemble of players in which mobile phone handsets are used both as sound sources and as hand-held controllers. Mobile phones are mounted in a specially devised pouch attached to a cord and physically swung to produce audio chorusing. During performance some players swing phones while others operate phones as handheld controllers. Wireless connectivity enables interaction between flying and hand-held phones using various bluetooth implementations. In one a dedicated mobile phone acts as a server that interconnects multiple clients, while in the other point to point communication takes place between clients on an ad hoc basis. Our presentation concludes with a comparative evaluation of scenarios that allow large numbers of non-expert musicians to play microtonal music. 1 Bluetooth Performance Scenarios Players swing mobile phones on a cord in a circular trajectory, as shown in Figure 1 (front left, rear rear). Each mobile phone is mounted in a pouch made of semitransparent fabric attached to a cord. As the phone is swung by its cord it produces audible artifacts such as Doppler shift and chorusing produced as a byproduct of movement. Bluetooth messages sent from hand-held phones control pitch parameters on flying phones (rear left, front rear). Two Bluetooth configurations have been used; in the first, three mobile phones interact with one another via a 'server' phone which relays control messages sent from any phone to every phone (Figure 2a), while in the second, each phone affects one other phone on an ad hoc basis (Figure 2b). Figure 2a. Mobile 'server' Figure 2b. Ad hoc connection 2 Pocket Gamelan - tools Several new tools have been developed and tested. 2.1 Scala exporter Microtonal tuning data, created using Scala tuning software, is exported and documented in Pure Data (Pd) using a purpose-built Scala command file. PD is then used to compose a work and emulate its performance on a single desktop machine prior to realization on phones. 2.2 pd2j2me Purpose-built tools are used to translate Pd files into JAR/JAD files, a format suitable for java phones. Pd2j2me is a library of j2me classes that allows composers working with Pure Data to create music that is exported to and performed on mobile phones. 2.3 Bluetooth In the first Bluetooth configuration, a 'server' makes connection to all phones; connection remains active throughout the performance. In the second, a connection is made between any pair of phones. During initialization, Bluetooth identifies all devices taking part. Clocks on each phone are synchronized during initialization. Bluetooth messages alter pitch parameters. We will perform examples of work produced to date, demonstrate tools used in their implementation, and discuss rationale and relative advantages of each configuration. 3 References Schiemer, G. and Havryliv, M. 2006 "Pocket Gamelan: tuneable trajectories for flying sources in Mandala 3 and Mandala 4" In Proceedings of the New Interfaces for Musical Expression Conference, Paris, France pp. 37-42 Figure 1. Hand-held phones control flying phones 43