# Design Dimensions of Co-Located Multi-Device Audio Experiences
## 2 Related Work  
Multi-device ecosystems and their applications are complex and encounter many additional challenges compared to their single-device counterparts. To tackle this complexity, and to enable the creation of more meaningful multi-device experiences, research has been conducted to increase our understanding, more broadly, of multi-device interactions and user behaviours. [PERSON] [6] presents a set of high-level design approaches to multi-device experiences, named the 3 Cs, which consist of _consistent_, _continuous_, and _complementary_ methods. These act as a practical guide for designing multi-device interactions for media experiences and provide a useful introduction for newcomers to the research space. As this research area has progressed and new prototypes have emerged, efforts have been made to consolidate the work through surveys and taxonomies. An excellent example of this is presented by [PERSON] et al. [3], who report on design characteristics, applications, tracking systems, and interaction techniques for multi-device systems. Moreover, for contemporary multi-device audiovisual systems, [PERSON] and [PERSON] [7] propose the term'media multiplicities' to describe coordinating systems of devices that interact to manifest media content and present four key affordances: _spatial_, where the devices are distributed in physical space; _scatterable_, where devices can move around and be reconfigured; _sensing_, devices can interact and coordinate using sensors; and _scalable_, where devices can be added and removed freely. While many of the discussed concepts can be applied in audio-only applications, most of the discussion is centered around multi-screen applications. This follows a common trend of research focusing on the visual modality, exploring applications such as'second screen' viewing [8; 9; 10] and augmented-reality TV [11; 12]. In addition, while many experiences are comprised of both visual and auditory stimuli, it is also valid to consider audio and visual experience aspects separately, due to the differences via which both of these modalities are perceived by the human body. The use of multiple devices for audio reproduction is most commonly applied in music-based performances, for instance, where the audience's devices are used as an array of loudspeakers. The bulk of this research occurred over the last decade with the rapid uptake of smartphones; however, this practice can be observed as far back as the 1970s, where analogue radios and cassette players have been used in experimental sound-art installations and exhibits [13; 14; 15]. Since then, mobile/laptop orchestras have been a popular avenue for speaker-array experimentation [4; 16]. [PERSON] [17] described designing these experiences as a 'wicked problem', where creators must design the instrument and the interactions between devices, as well as composing the music. To address this complexity, a prototyping and iteration design approach is commonly chosen [18]. With the proliferation of personal computing devices, a number of tools have been developed to reduce the difficulty in creating effective, cross-platform, multi-device audio experiences. _Soundworks_, for example, is a JavaScript framework for creating multi-device audio experiences for consumer devices and has been used in many demonstrations of participatory sound and music experiences [19]. _Audio Orchestrator_ is a production tool which allows producers to create multi-device audio experiences by facilitating audio routing to any number of devices through an allocation algorithm, which can be controlled through defined behaviours [20]. Using this tool, a number of trial productions have been made ranging from immersive audio dramas [21] to sports programs [22]. A final example is _HappyBrackets_, a programming environment for the creative coding of multi-device systems, that can also be used as a composition and performance tool for audio experiences [23].