The Composition & Performance of Spatial Music

A dissertation submitted to the University of Dublin for the degree of Doctor of Philosophy

Enda Bates

Trinity College Dublin, August 2009.

Department of Music & Department of Electronic and Electrical Engineering
Trinity College Dublin

 

To download the thesis in PDF format, click here.

 

 

 

Thesis Summary

One of the defining characteristics of electroacoustic music has been its use of technology to expand musical boundaries, whether through electronic processes in conjunction with traditional instruments, or through electronic processes alone. This characteristic allows parameters such as timbre and space to be examined in much greater detail, however, space is in many respects, fundamentally different from other musical parameters. Timbre relates to the spectral and temporal relationship between the components of an individual sound object, while rhythm, melody and harmony involve temporal and spectral relationships between sound objects. Space as a musical parameter is, however, much broader and more difficult to define. It incorporates the dimensions of individual sound objects, the relationships between sound objects, and even the relationship between the sound objects and the acoustic space in which they are heard. Furthermore, audible space itself can only become apparent through the temporal development of sounds themselves. Space as a musical parameter is therefore allencompassing and yet difficult to define. It incorporates every aspect of a sound, and yet the spatial aspects of a sound are often not consciously perceived as separate from the sound itself.

When I encountered spatial electronic music for the first time, I was immediately struck by the contrast between the dynamic movement of sounds in space in this music, and the static nature of the sounds and the performers at the concerts of electronic music I had encountered up to this point. I very quickly formed the opinion that spatialization was a critical and necessary aspect of electronic music, as the spatial movement of sounds provided a physicality and dynamism that greatly enhanced the listening experience. Indeed, multiple loudspeakers and spatialization was de rigueur in the earliest days of electronic music spatialization (see Figures 1 & 2).

 

 

 

 

 

 

 

 

 

 

 

 

 

As with many other composers, this early enthusiasm was quickly tempered by the experience of hearing my work performed for the first time outside of the studio over a large loudspeaker array. Much of the scientific research conducted in this area has focused on the ideal conditions of a single listener in an acoustically treated space. However, this optimum listening environment is quite different from a typical performance and results from these tests cannot be used to determine how these systems will perform in less than ideal conditions. In addition, much of the writing by composers of spatial music has discussed both the single listener and performance contexts and does not focus sufficiently on the differences between these two environments. This approach is also somewhat anachronistic considering the drastic decline in sales of music media in the modern era and the continued widespread enthusiasm for live performances.

The musical use of space exploits a fundamental aspect of hearing, namely our ability to locate sounds in space. However unlike other parameters such as pitch, rhythm and timbre, space is not usually an intrinsic aspect of the sound itself, and the movement of sounds through space is merely an illusion created through the careful blending of a number of static sources. A composer of spatial music cannot therefore treat this parameter in the same way as pitch or rhythm, and the technical details of how this illusion is created and maintained must be a fundamental and necessary part of the composer’s craft. In addition, how the spatial distribution of musical material affects the listener’s perception of that material is another critical aspect of spatial music composition. While numerous practical problems remain, there exists a body of empirical approach which can provide some justifiable basis for aesthetical decisions as to how and when space is used as a musical parameter. The empirical and systematic examination of spatialization techniques, particularly under the less than ideal conditions encountered during a performance, will
indicate their particular strengths, and importantly their limitations. In addition, the study of auditory perception and directional hearing can guide the compositional process and provide some indication of what the audience may actually hear during the eventual performance. The first half of my PhD thesis explores this issue in detail and provides a number of technical recommendations in terms of the strengths and weaknesses of the most commonly used spatialization techniques, such as stereophony, Ambisonics and wavefield synthesis.

An examination of various landmark works of spatial music reveals that different composers have developed many different ideas about the role of space in music. However, although many differences exist some general trends are evident. For example, a number of different composers have used spatial distribution to improve the intelligibility of different layers of independent and potentially dissonant musical materia, described beautifully by John Cage as the “co-existence of dissimilars” [Cage, 1957]. It is quite likely that this spatial distribution of the performers was first implemented merely to facilitate the performance of overlapping yet unrelated musical layers at different tempi or metres. However, there is also a significant amount of scientific research to suggest that a listener’s ability to detect and understand the content of multiple signals is indeed improved when the signals are spatially separated [Bregman, 1990; Shinn-Cunningham, 2003; Best, 2004]. Composers such as Charles Ives, Henry Brant and Karlheinz Stockhausen were clearly well aware of this fact, and they made extensive use of spatial distribution in their work for this reason.

The presentation of any work of spatial music to a distributed audience will necessarily result in certain members of the audience being situated outside the sweet spot. This will result in an unavoidable distortion in the spatial trajectory which is perceived by each member of the audience, and this distortion depends upon the position of the listener within the array. Moore suggested that the differences in perception among listeners are analogous to perspective distortion in photography or cinematography [Moore, 1983]. Although this is perhaps unsurprising, it raises significant questions about spatial music compositions which attempt to create and relate recognizable “sound shapes”. This form of spatial counterpoint, which McNabb describes as the motivic use of space, assumes that spatial locations and trajectories are clearly and unambiguously perceived by each listener [McNabb, 1986]. However the results of a very large number of empirical listening tests suggest that this is extremely difficult to achieve. Even in the case of point sources which are clearly localized, each listener will be orientated differently with regards to the loudspeaker array, and so will have a different perspective on the spatial layout. In this case it is very hard to see how spatial motifs can be clearly and unambiguously perceived unless they are restricted to very rudimentary movements. In the words of the composer Henry Brant, “Ideas of that kind seem to me more an expression of hope than of reality…. . It is hard enough to make the sounds do what you want “in sound” without saying that the sound should be shaped like a pretzel or something like that”. [Brant, 1967]

Complex spatial designs can perhaps be effective when used indirectly and this approach is somewhat reminiscent of other abstract processes which have been used to indirectly create and control complex textures in orchestral music. Consider this statement by Gyorgy Ligeti;
“Technically speaking, I have always approached musical texture through partwriting. Both Atmospheres and Lontano have a dense canonic structure. But you cannot actually hear the polyphony, the canon. You hear a kind of impenetrable texture, something like a very densely woven cobweb. The polyphonic structure does not come through, you cannot hear it, it remains hidden in a microscopic, underwater world, to us inaudible”. [Bernard, 1987]

In general, two distinct approaches to the use of space as a musical parameter have developed from the differing aesthetics which dominated mid-twentieth century electroacoustic composition. This dichotomy of an abstract syntax or an abstracted syntax [Emmerson, 1986], an organic structure or an architectonic structure [Harrison, 1999], has been discussed extensively by composers and theorists for the past fifty years, and is also clearly evident in electroacoustic spatial music. In this context, an abstract syntax involves the application of predefined spatial effects to different sources which may have been created specifically for this purpose, such as the serialist compositions of Stockhausen for example. In music which follows an abstracted syntax, such as diffusion concerts for example, a spatial strategy is derived from the sonic attributes of the source signal. Although diffusion is in certain respects somewhat limited in what it can achieve spatially, it is admirably focused on adapting each work for the particular performance space. Denis Smalley's theory of spectromorphology has its origins in the practice of diffusion, yet this
theory can equally be applied to other types of performances and aesthetics. Smalley describes gesture as an energy-motion trajectory which can be shaped by the composer through the manipulation of the attack and decay envelope of the sound object. The movement of the sound in space should therefore support and emphasize the inherent spectromorphological profile of the sound object, in other words, “the sounds tell you where they want to go” [Smalley, 2007]. A composition could therefore utilize either a gesture-carried structure which implies a degree of forward motion, triggered by some external impetus, or a texture-carried structure which focuses more on the internal activity of the sound which appears to act without any obvious external stimulus. In this way Smalley suggests that gesture and texture can be used as forming principles in a composition. This gestural approach does not require the listener to perceive and relate distinct locations or sonic trajectories, what matters instead are relative changes, i.e. the spectromorphological profile. Although different members of the audience may perceive different directions of movement, this will not fundamentally alter the overall gesture.

In conclusion, it would seem that space in a musical context is hard to define, and that the performance of spatial music is a significant challenge for composers of electroacoustic music. If a work is to be successfully transferred from the studio to the concert hall, the composer must be aware of the strengths and limitations of different spatialization techniques, and how these spatialized sounds will be perceived by the listener. Perhaps even more importantly, the spatialization strategy must be incorporated within the overall compositional aesthetic. The artistic control of space can undoubtedly add expressiveness to a musical performance, and this is particularly true of electronic sounds which lack a visual component. During an instrumental performance visible actions by the performer produces an audible result and it is this multi-modal feedback process that makes a performance “live”. The dynamic spatialization of electronic sounds can potentially replace or substitute for this missing visual component and provide a necessary and potentially thrilling physicality. However, this can only be achieved in a performance
context if the composer is fully aware of how their work will change when it is transferred from the studio to the concert hall.

Bibliography
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Problem, and His Solution”, Music Analysis, Vol. 6(3), pp. 207-236, 1987.

[Best, 2004] Best, V. A., “Spatial Hearing with Simultaneous Sound Sources: A
Psychophysical Investigation”, Doctoral Thesis, University of Sydney, 2004.

[Brant, 1967] Brant, H., "Space as an essential aspect of musical composition",
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[Bregman, 1990] Bregman, A. S., “Auditory Scene Analysis”, 196-200, pp. 204-250;
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[Cage, 1957] Cage, J., “Experimental Music”, Address given to the convention of
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[Emmerson, 1986] Emmerson, S., “The relation of language to materials”, The
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[Harley, 1998] Harley, M. A., “Spatiality of Sound and Stream Segregation in 20th-
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[Harrison, 1999] Harrison, J., “Sound, space, sculpture: some thoughts on the ‘what’,
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[McNabb, 1986] McNabb, M. “Computer Music: Some Aesthetic Considerations”,
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[Moore, 1983], Moore, F. R., “A general model for spatial processing of sounds”,
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[Shinn-Cunningham, 2003] Shinn-Cunningham, B. G., "Spatial hearing advantages
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[Smalley, 2007] Smalley, D., “Space-Form and the Acousmatic Image”,
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