Academic journal article Attention, Perception and Psychophysics

Do Metrical Accents Create Illusory Phenomenal Accents?

Academic journal article Attention, Perception and Psychophysics

Do Metrical Accents Create Illusory Phenomenal Accents?

Article excerpt

In music that is perceived as metrically structured, events coinciding with the main beat are called metrically accented. Are these accents purely cognitive, or do they perhaps represent illusory increases in perceived loudness or duration, caused by heightened attention to main beats? In four separate tasks, musicians tried to detect a small actual increase or decrease in the loudness or duration of a single note in melodies comprising 12 notes. Musical notation prescribed a meter (6/8) implying a main beat coinciding with every third note. Effects of metrical accentuation on detection performance were found in all four tasks. However, they reflected primarily an increase in sensitivity to physical changes in main beat positions, likely to be due to enhanced attention. There was no evidence of biases indicating illusory phenomenal accents in those positions. By contrast, and independent of metrical structure, pitch accents due to pitch contour pivots were often mistaken for increases in loudness.

In their seminal book on tonal music, Lerdahl and Jackendoff (1983) distinguished three kinds of accent: phenomenal, metrical, and structural. Phenomenal accents are conveyed by aspects of the physical sound structure, such as differences in loudness or duration, leaps in pitch, and temporal separation.1 Metrical accents, by contrast, are "a mental construct, inferred from but not identical to the patterns of accentuation at the musical surface" (p. 18). Structural accents are less relevant to the present study and can be left aside.

The perception of metrical structure in a musical rhythm rests largely on temporal regularity and the perception of phenomenal accents. For example, Povel (1984) and Povel and Essens (1985) developed a well-known theory of how perception of a beat is induced by a rhythmic pattern containing only temporal (grouping) accents created by the durations of intervals between events. More recently, Hannon, Snyder, Eerola, and Krumhansl (2004) and Ellis and Jones (2009), among others, have conducted detailed investigations of the relative importance of temporal and melodic (pitch) accents in the perceptual induction of meter. Meter consists of at least two hierarchically nested levels of beats, one of which (the main beat, or tactus) is most salient. After a metrical structure has been induced by a pattern of phenomenal accents, it tends to persist, making possible the perception of phenomena such as syncopation, offbeat accents, and hemiola. Musical sounds are considered to be metrically accented if they coincide with the main beat. London (2004, p. 23) puts it thus: "A metrical accent occurs when the metrically entrained listener projects a sense of both temporal location and relatively greater salience onto a musical event."

Phenomenal accents, although important, are not the only determinants of perceived meter. There are endogenous determinants as well, as is already suggested by the fact that an induced metrical structure can persist in the face of conflicting input. If the pattern of phenomenal accents is impoverished or ambiguous, the same musical passage can give rise to different perceived metrical structures. A classic example is the metrical perception of metronomic sequences that do not contain any phenomenal accents (apart from the temporally privileged first event, which tends to be perceived as metrically accented; see Brochard, Abecasis, Potter, Ragot, & Drake, 2003; Toiviainen & Snyder, 2003). Such sequences are often perceived as being in duple, triple, or quadruple meter, depending on their tempo and on the listener (Bolton, 1894). This form of metrical perception is entirely endogenous and reflects the listener's sensorimotor resonance to preferred beat periods in a broad region around 600 msec (Parncutt, 1994; Todd, Lee, & O'Boyle, 2002; Todd, O'Boyle, & Lee, 1999; Van Noorden & Moelants, 1999). Perception of different meters can also be induced deliberately, without changing the musical passage that is the object of perception. …

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