As would be expected, all four of Norman's principles are accounted for in the design of ScreenPlay , and their definitions and implementation will be discussed at length in the Methodology and Implementation chapter of the thesis. The use of metaphor in particular is of vital importance in imparting control over the topictheoryinspired transformative algorithm that underpins the system designmodel.
2.7 Timbre and Spectromorphology
As has been touched upon previously, Xenakis influenced by the work of his teacher, Messiaen, in which 'colour and texture frequently predominate over pitch' (Matossian, 1986, p. 61) focussed a great deal of attention on the use and manipulation of timbre in his works; as opposed to an overreliance on purely tonal and rhythmic characteristics to shape a composition. Specifically, in his work Metastaseis (195354), Xenakis implemented traditional articulation techniques such as glissando, pizzicato etc. in a nontraditional way 'by scoring them for large sections of the orchestra playing en masse at varying speeds, on different pitches, in aggregates or various combinations to achieve the textural fields fundamental to the nonhierarchic and multidirectional character of the music' (Matossian, 1986, p. 61; Xenakis, 1992, pp. 910). While similar compositional techniques were also applied in a number of his other works (1992), as well as exploring the use of timbre in vocal music through the use of phonemes and syllables in Nuits (1967; Matossian, 1986, pp. 207208; Souster, 1968), he also applied the inverse of this textural/timbralcentric approach when composing Herma (196061), in which he purposefully limited and/or removed the use of different modes of attack, accents and rhythmic elements in favour of applying sieve theory to pitchselection. The omission of these features, ultimately, was not detrimental to the resulting musical work; however, ordinarily 'it is these very choices which produce a living music, closely tailored to the instrument instead of a dry sampling of pitches which might have been the result of such a system in other hands' (Matossian, 1986, p. 156). The values texture and timbre brought to orchestral music were also appreciated by Varèse, who
experimented with 'Effects like timbral shifts in a single note, or complex attacks created by pitched and nonpitched instruments simultaneously … as well as a very special concern with dynamics that could be compared to the techniques of amplitude envelope shaping in electroacoustic music.' (Guedes, 1996, p. 7)
As a theoretical approach to analysing the textural and timbral qualities within music, or more specifically, 'the interaction between sound spectra … and the ways they change and are shaped through time' (1997, p. 107), Denis Smalley developed the concept of spectromorphology . Spectromorphological analysis/evaluation is chiefly concerned with the ideas of sourcecause interaction , source bonding and sounding gesture all three of which are linked. Through use of the spectromorphological referral process (reversal of the sourcecause interaction chain) (p. 111) the listener is able to attempt to identify both the soundingbody and gesturetype used to create any given sound. 'in traditional music, soundmaking and the perception of sound are interwoven, in electroacoustic music they are often not connected' (p. 109) and, thus, analysis/identification of the sourcecause interaction properties of a sound can be more difficult. However, the concept of technological listening (again, attributed to Smalley), whereby the technology or technique behind a sound/piece of music is perceived by the listener as opposed to the music itself, is often applied by the listener (consciously or otherwise) to the process of spectromorphological analysis within the context of electronic/electroacoustic musics (p. 109).
Source bonding , 'the natural tendency to relate sounds to supposed sources and causes, and to relate sounds to each other because they appear to have shared or associated origins' (p. 110) is reliant upon what Smalley calls intrinsic and extrinsic "threads". Intrinsic threads can be defined as 'sound events and their relationships as they exist within a piece of music', while the extrinsic relate to the 'foundation in culture' outside of a musical work that allows the intrinsic thread to exist/have meaning (p. 110). According to Smalley, 'intrinsic spectromorphological description … should be capable of helping a listener to pinpoint those musical qualities which are carriers of meaning.' (p. 111)
Sounding gesture is the association of sounds with their likely sources that are culturally embedded in the consciousness of the listener, much like the learned cultural conventions upon which Structuralist binary opposition models are founded. As the likelihood that a soundsource will be recognisable from the sound itself becomes more and more remote, Smalley refers to his concept of gestural surrogacy . Firstorder surrogacy relates to instances in music where both the soundsource and gestural cause of a sound are
recognisable when hearing it. Secondorder surrogacy deals primarily with 'traditional instrumental gesture', although it also applies to instrumental simulation. Thirdorder surrogacy is adopted by a sound when the reality of its source and/or gestural cause are difficult to distinguish by the listener upon hearing it. Finally, there is remote surrogacy , which applies only when both the 'Source and cause become unknown and unknowable as any human action behind the sound disappears' (p. 112). Related to gestural surrogacy as a mode of musical analysis and, in particular, third and fourthorder surrogacy, is the idea that 'If gestures are weak, if they become too stretched out in time, or if they become too slowly evolving, we lose the human physicality. We seem to cross a blurred border between events on a human scale and events on a more worldly, environmental scale' (p.113). Because of this Smalley concludes that 'A music which is primarily textural, then, concentrates on internal activity at the expense of forward impetus.' (pp. 11314)
Despite the textural/timbral shaping of ScreenPlay 's musical output carried out by the topictheoryinspired transformations the theories relating to spectromorphology discussed thus far do not directly influence the design but, instead, are passively relevant through the way in which they present a general association with all musics in particular those which depend heavily on synthesized and sampled/resampled, or "nonhuman", sounds (traditional instrumentalism could also be described as nonhuman, but these sounds and their associations are much more culturally ingrained than the wide variety of textural/timbral possibilities related to electronic soundcreation) such as electronic and electroacoustic music. The same is true of other topics touched upon by Smalley, such as audience anticipation when listening to music (pp. 112115) and motion and growth processes (pp. 115117) within the context of electroacoustic music where 'traditional concepts of rhythm are inadequate to describe the often dramatic contours of electroacoustic gesture and the internal motion of texture which are expressed through a great variety of spectromorphologies' (p. 115). Smalley also covers a few other areas specific to how humans hear pitch differences and the movement between them, as well as electroacoustic music, which are, again, not directly applicable within the context of ScreenPlay .
There are, however, certain concepts outlined in Smalley's work that bear a great deal more relevance to ICMS design, and that of ScreenPlay in particular. For instance, there exists a direct connection between the four qualifiers of spectral space described by Smalley (emptinessplenitude, diffusenessconcentration, streamsinterstices, overlapcrossover) in particular the first two with the application of topical oppositions made available to the
user(s) by ScreenPlay in order to encourage creative expansion and structural development in both composition and performance (p. 121), and in which texture/timbre also play an important role. Additionally, there are considerations to be made in terms of ICMS installation design when related to Smalley's theory of space and spatiomorphology 'Spatial perception is inextricably bound up with spectromorphological content' 'higher pitches can be thought of as spatially higher, and lower pitches lower' (p. 122), which is applicable to ScreenPlay because it can exist as both a collaborative, interactive installation focussed on group improvisation in electronic music, as well as studio compositional tool to aid in the creative process. Also of interest when discussing ICMS installation design is the differentiation between the composed space ('the space as composed on to recorded media' (p. 122)) and the listening space . The listening space can be divided into two categories: personal, where the listener is generally close to and directly facing the soundsource; and public, where the 'listener could be in any one of a variety of distant or offcentre positions relative to a frontal referenceimage [or within a multichannel installation].' In any case, 'spectromorphology becomes the medium through which space can be explored and experienced. Space, heard through spectromorphology, becomes a new type of "source" bonding.' (p. 122)