The Limits of Perceptual Phasing
Researchers in the field of music perception have written about the term “phase”, but how does this relate specifically to music. Phase can be described as “the difference between the expected time of an onset of sound and the time when it actually occurs, in relation to the period between two expected onsets.” It is not just a single onset that can be phased, but short series of onsets that create perceptual continuums also known as streams (Bregman, 1990).
Applied within a musical context, phase could encapsulate a stream that is in cannon with itself (the start of the 2nd stream would occur at a logical metrical location), to streams phasing 100-300ms with itself. Some studies indicate that listeners are able to differentiate between streams while they are in phase, but these are at slower tempi. Where does our ability to differentiate streams break down, and what are the key elements that eliminate or enable this ability?
The use of phasing in music goes back as far as the 15th century with composers like Josquin des Prez among his contemporaries mimicking their vocal lines with other vocal parts in a sort of faux-canon called imitative counterpoint. This compositional technique to achieve comprehensive counterpoint continued through the centuries. However, it has only been in the last 50 years of history that composers have utilized phasing in a much more precise way. In his 1995 composition Piano Phase, composer Steve Reich utilizes phase on a micro level. What are the elements that allow us to differentiate streams within 15thcentury compositions and other simple childhood songs and canons (e.g. Row, Row, Row your boat), but make it seemingly impossible to differentiate streams in a piece like Piano Phase?
Wilson, S. (2000). Pattern perception and temporality in the music of Steve Reich: An interdisciplinary approach (Doctoral dissertation). Available at UNSWorks http://handle.unsw.edu.au/1959.4/44991.
Abstract: Examines pattern perception and temporality in the music of Steve Reich. The temporal experience of Reich’s music is significantly influenced by how a listener’s perceptual ordering faculties respond to the ambiguous pattern structures which characterize much of his work. The potential for research in auditory perception to provide insights into the temporal nature of Reich’s music is evaluated, and the ways in which resulting patterns participate in the perception and cognition of his music are investigated. The interdisciplinary approach adopted in this research responds to the lack of information on Reich’s music, and a prevailing view among musicologists that his compositions resist conventional analysis. Beat class analysis is applied to Reich’s phase shifting music to consider evidence for internal progressive structures.
Bregman, A. (1990). Auditory scene analysis: The perceptual organization of sound. Cambridge: MIT Press Cambridge, MA.
Abstract: Discusses timbre as both cause and effect of perceptual organization. The influence of pitch frequencies and the spatial separation and integration of sounds on the human perceptual mechanism is also described. Consonance and dissonance are both described as timbral phenomenon.
Epstein, P. (1986). Pattern structure and process in Steve Reich’s Piano phase. The Musical Quarterly, 72(4), 494-502.
In Steve Reich’s minimalist composition Piano phase (1967), a 12-beat pattern is gradually rotated against itself. This continuous, unedited phasing process yields composite patterns largely predictable from the structure of the original pattern. Yet the richness of the piece derives from the unpredictably discontinuous way in which these resultant patterns are perceived to change and from the variety of strategies available to the listener for shaping the musical experience.