3.1 The 11 Criteria for Collaborative Musical Interface Design
A large part of the development of ScreenPlay involved the incorporation into its design of some key elements collated from a number of well established ICMSs, whilst simultaneously aiming to address the deficiencies exhibited by these systems in relation to the theoretical and conceptual approaches to ICMS design against which they were scrutinized. One concept taken into consideration was Blaine and Fels' 11 criteria for collaborative musical interface design (2003), for which below has been provided a full breakdown and explanation of each:
1. Focus : The efforts made to increase the audience's "transparency" (Fels, Gadd & Mulder, 2002) i.e. the ease with which members of the audience are able to discern the connection between the actions of the user(s)/performer(s) when interacting with the system and the resulting musical output. 'Generally with novice participants, the sound generated within collaborative musical environments is intended for the players' (Blaine & Fels, 2003, p. 414), but Blaine and Fels also note that, if it is the intention that the musical output should be such that it can be appreciated by a wider audience, then this "transparency" becomes essential.
2. Location : The impact had by the location of an ICMS's interface(s) on the ability of users/performers to learn from each other how best to interact with the system in terms of the relationships between certain gestures and their corresponding sonic events and sequences i.e. whether the UIs are 'colocated' (sharing the same performancespace) or randomly distributed 'over a network [at] nonspecific locations' (p. 417), as is often the case with "Computer Network Music" systems (Early Computer Network Ensembles, n.d.; Brown, n.d.) that are reliant upon the internet to connect multiple players.
3. Media : The use of audiovisual elements within the interactive system 'as a way of
enhancing communication and creating more meaningful experiences … by
reinforcing the responsiveness of the system to players' actions', as well as the increased potential for '[distracting] players from seeing other players' actions, or from attending to aural elements' (Blaine & Fels, 2003, p. 417), which can ensue as a result of overemphasis on the visual aspect of a system's response to the user(s).
4. Scalability : The constraints imposed upon the depthincontrol afforded to the users/performers by the UI over the generated musical output of a system, resulting
from the number of individuals by which the system is intended to be used simultaneously and vice versa. 'An interface built for two people is generally quite different from one built for tens, hundreds or thousands of players.' (p. 417)
5. Player interaction : The effects of providing each participant in a collaborative interactive system environment with either the same, similar or differing UIs. An increased presence of identifiable similarities between the interfaces of all performers can 'lead to a more relaxed environment and more spontaneous group behaviours' (p. 417) as a result of an improved collective understanding of what each individual is contributing to the overall auditory experience.
6. Musical range : The need to strike the correct balance when limiting the range of freedom afforded to the player(s), in terms of melodic/harmonic chromaticism and the authority of quantizing rhythmic input etc., so as to allow substantial room for improvisatory expression, flair and embellishment while ensuring the resulting musical output generated by the system is coherent, pleasurable, and provides a sense of satisfaction to novice users lacking in musical knowledge and experience.
7. Physical interface/sensor : The importance of implementing a suitable means of interfacing with the system, be it tangibly through touch and pressure sensors or gesturally via motion capture and/or bodymounted motion sensors. This is what defines the affordances of a system.
8. Directed interaction : The decision whether or not to provide the user(s) with guidance as to more effectively and efficiently interacting with the system and/or each other through it by way of the presence in the performance space of a trained instructor or, alternatively, more rigid performance structures, such as the implementation of a "call and response" scheme with definitive roles for "leaders" and "followers" within the group; as well as consideration of how enforcing such a system would impact upon the overall interactive experience.
9. Learning curve : 'an evaluation of the tradeoff between speed of learning and musical constraints' (p. 418). The task of fulfilling the requirements of providing an engaging and satisfying musical experience for novices and firsttime users, while leaving scope for improved and more virtuosic interactions with practise in order to captivate the player(s) beyond the point of initial intrigue and exploration of a system's functionality and architecture.
10.Pathway to expert performance : The advantages of providing the user(s) with experiencedependent "modes" such as novice, intermediate and expert, which become incrementally less restrictive and thus maximise the possibility for freedom of expression in performance but also for userinput error and mistakes a system very much like that of selecting the difficulty level of a computer game.
11.Level of physicality between players : The effect of requiring users/performers to physically collaborate with each other by working together in order to fully exploit the potentialities of the ICMS, and the impact this can have on the levels of engagement with the system and sonic/performative experience felt by individuals within the group. 'Most often, it is not the interface itself that makes for an engaging, satisfying experience, but the group ambience and development of synergistic relationships between players that leads to positive communal experiences.' (p. 419)
The gridbased design of the playing surface on ScreenPlay 's GUI (as seen in Fig. 2) is inspired by that of the Ableton Push (2013) and, as such, allows users to "lock" the pitchintervals between individual "pads" on the buttonmatrix to those of a specific scale. The notes of the scale are assigned to the "pads" of the inputmatrix from the left to right; but also so that, for every 3 notes ascending along the horizontal row, the 3 positioned directly above continue that ascent, thus allowing for any standard triad within the chosen key signature/scale to be formed using the same handshape anywhere on the grid. In addition, the "pads" to which the rootnotes of the scale are assigned are clearly displayed through the use of a different background colour to that used by the rest of the "pads", providing the player(s) with a frame of reference that enables them to orientate themselves with greater accuracy when interacting with the playing surface (see Fig. 3). This is in coordination with the guidelines for musical range as outlined in Blaine and Fels' 11 criteria, by ensuring a pleasurable, satisfying and immersive experience for novice and firsttime users lacking in prior musical knowledge; while the ability to enable record quantization at a value of 1/4, 1/8 or 1/16 also serves to fulfil this criterion. Key selection is facilitated by way of a selection matrix (Fig. 4), with the rootnote of the key denoted by the position of the selectionmarker in relation to the xaxis and the scale/mode denoted by the marker's position on the yaxis the scales/modes that are available for selection are: Major, Minor, Dorian, Phrygian, Lydian, Mixolydian, Aeolian and Locrian.