|Vol. 34 Issue 2 Reviews||Reviews > Multimedia >|
Barry Truax: Acoustic Communication and Compositional Techniques
DVD-ROMs (2), 2008/2009, CSR-DVD 0801/ CSR-DVD 0901; available from Cambridge Street Records, 4346 Cambridge Street, Burnaby, British Columbia V5C 1H4, Canada; electronic mail firstname.lastname@example.org; Web www.sfu.ca/~truax.
Reviewed by Mary Simoni and Kristin Fosdick
A newly-released interactive double DVD-ROM Acoustic Communication & Compositional Techniques by Barry Truax is a compelling teaching tool for computer music theory and composition that uses text, images, and sound examples to explore micro-level sound. The juxtaposition of mixed media imparts a glimmer into the theoretical, compositional, and stunning influences that inspire his formidable work. The first DVD-ROM is organized into sections called Microsound and Granular Synthesis, Granulation of Sampled Sound, Karplus-Strong Resonators and Comb Filters, Convolution, and Analysis of Specific Pieces including Riverrun (1986/2004) and The Shaman Ascending (2004-05). The second DVD-ROM includes sections on Soundscape Composition and Acoustic Space and additional analyses of compositions by Mr. Truax including Pendlerdrøm (1997), Island (2000), Temple (2002), Dominion (1991), and Chalice Well (2009). Complementary websites hint at the content included on the DVD-ROMs (www.sfu.ca/~truax/riverdvd.html and www.sfu.ca/~truax/scompdvd.html). These DVD-ROMs succeed Mr. Truax’s CD-ROM entitled Handbook for Acoustic Ecology (1999).
The section on micro-level sound design begins with a diagram that relates the time domain and frequency domain with the Fourier transform and inverse Fourier transform connecting each domain. Mr. Truax states that at the level of micro-sound, time, and frequency are interdependent and linked by an Uncertainty Principle defined as:
?t ≥ 1/?f
He relates this Uncertainty Principle to the Heisenberg Uncertainty Principle that states that certain pairs of physical properties, like position and momentum, cannot both be precisely known; the more precisely one property is known, the less precisely the other can be known. Mr. Truax creates the analogy with the Heisenberg Uncertainty Principle to make the point that a change in the time domain results in a change in the resultant spectrum. A lecture or supplementary reading that clearly explains the concepts should support the potent content of these slides.
Mr. Truax juxtaposes the extremes of frequency and time pictorially, explaining that discrete frequency assumes that the Fourier analysis is performed on a signal that lasts forever, e.g. infinite time. An impulse in time can be precisely measured, but a Fourier analysis may result in a multitude of frequencies (e.g. infinite bandwidth). Following the graphic relationship of time and frequency, he provides a diagram from Dennis Gabor’s landmark 1947 article, “Acoustical Quanta and the Theory of Hearing.” The diagram, without citation, depicts a Gaussian envelope applied to a window of a Fourier transform that produces a Gaussian envelope for the real part (frequency) of an analysis. Finally, he correlates the range of human hearing to our capacity to distinguish individual grains when those grains are temporally spaced at a time interval of 50 msec or more. As the grains become more closely spaced in time, the discrete events fuse into a complex timbre.
Granular synthesis is presented first historically, then in the context of the grain itself and the grain envelope. Various grain envelopes are presented visually, as well as three common types of granular synthesis: quasi-synchronous, asynchronous, and pitch-synchronous. There are 15 sound examples that increase in difficulty from a sinusoidal granular texture to phonemes that progress from a synchronous to asynchronous texture. These examples incrementally change variables such as frequency range, duration, and delay so that the listener can readily perceive the effect of specific variables on the resultant timbre.
Granulation of sampled sound is briefly defined as a technique that divides the (sampled) sound into short enveloped grains of 50 msec duration or less, and reproduces them with densities ranging from several hundred to several thousand grains per second. Mr. Truax has effectively used granulation of sampled sound through the development of his PODX system. Granulation of sampled sound is used in many of his compositions, such as The Wings of Nike (1987) and Tongues of Angels (1988). However, since 1990, longer sequences of environmental sound have been used in pieces such as Pacific (1990), Dominion (1991), Basilica (1992), Song of Songs (1992), Sequence of Later Heaven (1993), Sequence of Earlier Heaven (1998) and the opera Powers of Two (1995-99). In this section, Mr. Truax provides additional links to diagrams for FOF Synthesis (formant waveform), sound examples of FOG synthesis (formant grains) by Michael Clarke from the University of Huddersfield, diagrams of VOSIM (voice simulation), and complex systems including links to chaotic non-linear dynamical systems, cellular automata, and genetic algorithms.
Mr. Truax’s discussion of waveguide resonators begins with a description of the Karplus-Strong algorithm. He describes the resonances of waveguides and explores the timbral relationships between their delay line and the loop time of a comb filter. This section links to a section on phasing that includes a definition and a block diagram, as well as verbal and graphic explanations. The author provides some historical reference to the first observation of phasing in 1693. He also contrasts explanations of phasing, reverberation, and echo by stating the relative range of delay time that causes the effect, providing specific time values for phasing (flanging) at 10-25 msec. He makes a distinction between chorusing (applying sub-audio modulation to delayed/summed signals) and choral effects. These explanations include both sound examples and compositional excerpts.
After a succinct exposition of convolution, Mr. Truax provides an explanation of convolving dry signals with impulse responses of physical spaces to achieve a reverberation aesthetic. Audio samples of singing and speaking are convolved with impulse responses from various reverberant spaces, including cathedrals and performance spaces. The section explicates both “auto-convolving,” the convolution of a signal with itself, and the process of convolving two signals together. Examples of dry sounds convolved together, and with themselves, include bassoon, cello, and speech samples. The author continues with a characterization of the resultant timbres, including phenomena like the smearing of attack transients and the tendency of several sound editing programs to boost high frequencies in convolved signals. Particularly intriguing in the soundfiles included on the disc are convolutions of a bassoon sample with John Cage speaking, as well as a cistern impulse response convolved with Pauline Oliveros’ Deep Listening. Other soundfiles include convolved speech examples that are convolved again with other speech examples. Listeners can quickly ascertain the power of convolution as a compositional technique through the variety of sounds and timbres that are realized in these carefully selected sound examples.
The analysis of specific pieces on the first DVD-ROM includes Riverrun (1986/2004) and The Shaman Ascending (2004-05). The analysis of Riverrun is based on the breathtaking 2004 octophonic version that is well documented. The source materials, spatialization methodology, and production score are referenced on the DVD-ROM, making the DVD-ROM an excellent teaching tool.
The second DVD-ROM begins with an explanation of soundscape composition and its relationship to R. Murray Schafer’s World Soundscape Project. The guiding principles of soundscape composition include the listener’s ability to recognize the source material and that sound invokes the listener’s knowledge of an environmental and psychological context. Additionally, the composer’s knowledge of environmental and psychological contexts shapes the micro- and macro-formal elements of the composition. Lastly, soundscape composition enhances our understanding of the world and influences our daily perceptual habits. At a time when our environment is threatened by pollution, this approach to composition exalts human creativity to passionate environmental activism.
The analyses of the compositions provide a thorough and cogent exhibition of Mr. Truax’s compositional process and include a wealth of supporting documentation including program notes, a structural overview, accompanying spectrograms with temporal references, description of source materials, production notes, reviews, and references. These sections of the second DVD-ROM are priceless snapshots of the composer’s creative and technological prowess.