This issue of Organised Sound focuses on mapping in computer music. Unlike many issues of the journal, all articles in this edition are related to the theme. The call for contributions resulted in a significant collection of work which covered a broad range of activity in the field. This number of articles would normally fill more than one issue of the journal but we decided to keep the collection together as a representative body of work.

We were delighted to welcome Marcelo Wanderley as Guest Editor for this issue. I would like to thank him for his hard and diligent work throughout the preparation of this issue.

Software-based musical instruments have controls for input, a sound synthesizer for output, and mappings connecting the two. An effective layout of controls considers how many degrees of freedom each has, as well as the overhead of selecting each one while performing. An isolated mapping from one control to one synthesis parameter needs an appropriate choice of proportional, integral or derivative control (the control's value, or that value's rate of change, drives the synthesis parameter's value, or that value's rate of change). Beyond this, a compound mapping cross-coupling several controls and synthesis parameters can surprisingly increase the performer's intuitive understanding of the instrument.

This paper considers the issues involved in the design of electronic and computer interfaces, specifically mapping - the designed link between an instrument's playing interface and its sound source. It defines the problem area, reviews the literature, and gives examples of specific system mappings. A general model is presented, with the aim of providing a framework for future discussions on what makes an effective mapping. Several guidelines for mapping strategies are given, based on existing work.

We define a two-axis transparency framework that can be used as a predictor of the expressivity of a musical device. One axis is the player's transparency scale, while the other is the audience's transparency scale. Through consideration of both traditional instruments and new technology-driven interfaces, we explore the role that metaphor plays in developing expressive devices. Metaphor depends on a literature, which forms the basis for making transparent device mappings. We examine four examples of systems that use metaphor: Iamascope, Sound Sculpting, MetaMuse and Glove-TalkII; and discuss implications on transparency and expressivity. We believe this theory provides a framework for design and evaluation of new human–machine and human–human interactions, including musical instruments.

This paper is about mapping strategies between gesture data and synthesis model parameters by means of perceptual spaces. We define three layers in the mapping chain: from gesture data to gesture perceptual space, from sound perceptual space to synthesis model parameters, and between the two perceptual spaces. This approach makes the implementation highly modular. Both perceptual spaces are developed and depicted with their features. To get a simple mapping between the gesture perceptual subspace and the sound perceptual subspace, we need to focus our attention on the two other mappings. We explain the mapping types: explicit/implicit, static/dynamic. We also present the technical and aesthetical limits introduced by mapping. Some practical examples are given of the use of perceptual spaces in experiments done at LMA in a musical context. Finally, we discuss several implications of the mapping strategies: the influence of chosen mapping limits onto performers' virtuosity, and the incidence of mapping on the learning process with virtual instruments and on improvisation possibilities.

Mapping concerns the connection between gestures, or structures and audible results in a musical performance or composition. While this is of intense interest to performers of new instruments and instrument designers, it has also been an area of interest for some composers. Algorithmic composition is sometimes the process of imagining a gesture or structure - perhaps physical or visual - and then applying a mapping process to turn that ‘gesture’ of the conceptual domain into sound which may display the original conception in some way. This article looks at mapping from the point of view of algorithmic composition, particularly where persistence is an issue, such that the gesture (conceptual domain) is embodied and perceptible in the musical result.

This paper describes the interactive strategies adopted during the composition and realisation of construction 3 for soprano saxophone and multiple media, by Tony Myatt and Peter Fluck. This work is an interactive multiple media composition for computer, computer-enhanced saxophone and computer graphics projected onto irregularly shaped screens. Derivation of the performer sensing system and mapping strategies to control signal processing, computer generated materials and communication gestures between the performer and computer are described. These processes include generative mapping techniques using neural networks for the recognition of gestural information and the development and application of wireless, wearable sensing technology. This work is described as a holistic approach to the derivation of performer sensing, data mapping and the application of reactive and interactive processes in the context of the creation of a new musical and multiple media composition.

In this paper we describe a new way of thinking about musical tones, specifically in the context of how features of a sound might be controlled by computer musicians, and how those features might be most appropriately mapped onto musical controllers. Our approach is the consequence of one bias that we should reveal at the outset: we believe that electronically controlled (and this includes computer-controlled)musical instruments need to be emancipated from the keyboard metaphor; although piano-like keyboards are convenient and familiar, they limit the musician's expressiveness (Mathews 1991, Vertegaal and Eaglestone 1996, Paradiso 1997, Levitin and Adams 1998). This is especially true in the domain of computer music,in which timbres can be created that go far beyond the physical constraints of traditional acoustic instruments.

This paper describes a trans-domain mapping (TDM) framework for translating meaningful activities from one creative domain onto another. The multi-disciplinary framework is designed to facilitate an intuitive and non-intrusive interactive multimedia performance interface that offers the users or performers real-time control of multimedia events using their physical movements. It is intended to be a highly dynamic real-time performance tool, sensing and tracking activities and changes, in order to provide interactive multimedia performances.

From a straightforward definition of the TDM framework, this paper reports several implementations and multi-disciplinary collaborative projects using the proposed framework, including a motion and colour-sensitive system, a sensor-based system for triggering musical events, and a distributed multimedia server for audio mapping of a real-time face tracker, and discusses different aspects of mapping strategies in their context.

Plausible future directions, developments and exploration with the proposed framework, including stage augmenta tion, virtual and augmented reality, which involve sensing and mapping of physical and non-physical changes onto multimedia control events, are discussed.

The Metasaxophone is an acoustic tenor saxophone retrofitted with an onboard computer microprocessor and an array of sensors that convert performance data into MIDI control messages. The instrument has additionally been outfitted with a unique microphone system that allows for detailed control of the amplified sound. While maintaining full acoustic functionality it is also a versatile MIDI controller and an electric instrument. A primary motivation behind the Metasaxophone is to put signal processing under direct expressive control of the performer. Through the combination of gestural and audio performance control, employing both discrete and continuous multilayered mapping strategies, the Metasaxophone can be adapted for a wide range of musical purposes. This paper explores the artistic and technical development of the instrument, as well as new conceptions of musical mappings arising from the enhanced interface.

The vBow, a virtual violin bow musical controller, has been designed to provide the computer musician with most of the gestural freedom of a bow on a violin string. Four cable and servomotor systems allow for four degrees of freedom, including the lateral motion of a bow stroke across a string, the rotational motion of a bow crossing strings, the vertical motion of a bow approaching and pushing into a string, and the longitudinal motion of a bow travelling along the length of a string. Encoders, attached to the shaft of the servomotors, sense the gesture of the performer, through the rotation of the servomotor shafts, turned by the motion of the cables. The data from each encoder is mapped to a parameter in synthesis software of a bowed-string physical model. The software also sends control voltages to the servomotors, engaging them and the cables attached to them with a haptic feedback simulation of friction, vibration, detents and elasticity.