Virtual Slide Guitar

Abstract

This article describes a system for virtual slide guitar playing. From the control point of view, it can be seen as a successor of the virtual air guitar (VAG) developed at Helsinki University of Technology (TKK) a few years ago (Karjalainen et al. 2006). The original VAG allows the user to control an electric guitar synthesizer by mimicking guitar-playing gestures. In the current work, the same gesture-control approach that was found successful in the VAG is used: a computer-visionbased system, in which a camera detects the player's hands and a computer tracks the hand movements and converts them into control data, such as pluck events and string length. Sound synthesis in the virtual slide guitar application is based on an energy-compensated time-varying digital waveguide model of a guitar with new extensions to generate contact sounds caused by the slide tube touching the strings. Video files showing the virtual slide guitar in action can be found on the accompanying Web page (www.acoustics.hut.fi/publications/papers/vsg/) and the forthcoming 2008 Computer Music Journal Sound and Video Anthology DVD. Although the current implementation uses a camera-based user interface, it can also be controlled by other humanmachine interfaces or computer programs. Excellent reviews on gestural control of music synthesis have been written by Paradiso (1997) and by Wanderley and Depalle (2004). Camera-based gesture analysis has become very sophisticated owing to increased computing power and new methodologies provided by research, as exemplified by the EyesWeb platform (Camurri et al. 2000, 2005; Gorman et al. 2007). Digital waveguide modeling is mature technology, which can be applied to high-quality synthesis of various musical instruments (Smith 1992; Valimaki et al. 2006). For more information on waveguide synthesis of string instruments, see Valimaki et al. (1996), Karjalainen, Valimaki, and Tolonen (1998), and Karjalainen et al. (2006). The roots of this study are in an early prototype of the TKK virtual air guitar, which here is called the rubber-band virtual air guitar. It was a simplified gesture-control system, in which the distance between the hands was detected and di-