Tracking Musical Patterns Using Joint Accent Structure

Tracking Musical Patterns using Joint Accent Structure MARIRIESS JONES AND PETER Q. PFORDRESHER The Ohio State University Abstract Joint Accent Structure (jAS) is a construct that lengthened tones and/or rests. uses temporal relationships between different accents in a Much research has been directed toward understanding melodic pattern as indices of its complexity. Concordant the effects of single accent types (e.g., melodic only) on the patterns are ones in which the periodic recurrence of perception of musical events. In contrast, we know little melodic accents form simple ratios with the period of about the temporal coherence of more intricate patterns temporal accents (e.g., 1:1, 1:2), whereas Discordant that result from combinations of different accent types. patterns have periods of melodic and temporal accents Indeed, the relationships between different accents in time with a more complex accent period ratio (e.g., 3:2). may contribute to the temporal coherence of a pattern. Participants were told to selectively attend to and synchro- When different accent types combine in a musical event, nize finger taps with accents in two experiments that they outline a time structure that has been termed that examined attentional tracking to musical patterns having event's "Joint Accent Structure" (Jones, 1987, 1993). a "concordant" or "discordant" JAS. Results indicated that Different Joint Accent Structures (jAS's) result when the tapping was more variable with discordant than with positioning of accents form different higher order time concordant JAS patterns, both with respect to produced relationships. The present research examines the role of inter-accent time periods and with respect to the phase of different JAS's in real time attending to simple musical taps relative to accent onsets. These findings are inter- events. preted in terms of real time attending and its control by We suggest that listeners who are sensitive to accented event time structure. relationships respond directly to time intervals between various accents within a JAS, and may use higher-order invariant aspects of this time structure to guide attending In listening to music one often experiences a sense of in a preparatory fashion. In this way a JAS enables listeners temporal anticipation that is crucial to the impact of a to monitor unfolding events in time. Consider, for piece. We contend that part of this experience derives instance, the first few bars of Beethoven's fifth symphony from the establishment of regular accent relationships in shown in Figure 1. The fourth note of the piece receives that piece. An accent may be defined as any element in an an accent from two different sources: an increase in auditory sequence (e.g., a tone) that stands out from duration (a temporal accent) and a change in pitch (a others, usually because it disrupts the context established melodic accent). For this excerpt, the Joint Accent Struc- by surrounding elements (e.g., it is longer in time or ture created by the co-occurrence of a temporal and a higher in frequency). Accents arise from changes along melodic accent provides a clear time structure, one different specifiable dimensions (such as time or fre- characterized by a strongly marked and recurrent time quency); we refer to an accent defined by a change along period. This invariant periodicity, in turn, creates a strong one dimension as a distinct accent "type." Instances of expectation for future accents, which Beethoven fulfills in various accent types may mark out distinct time periods the next several measures. within a musical event, lending to it a coherent temporal The preceding example outlines a relatively simple JAS. structure. For example, a coherent melodic line may Here, two different accent types (melodic, temporal) designate regularly occurring melodic-type accents by coincide to outline a common recurrent time period. In virtue of changes in contour, pitch distance or implied more complex JASs, different accents specify different, harmony, as this information arises from distinct move- possibly conflicting, time relationships. When such time ments of pitch in time. Similarly, a melody's rhythm may relationships conflict, the accent types involved may designate a series of temporal-type accents through neither coincide in time nor outline the same recurrent Canadian Journal of Experimental Psychology, 1997,51:4,271-290 272 Riess Jones and Pfordresher Opening Motif for Beethoven's 5th Symphony Melodic Accent Types 2a: Melodic Contour "Pivot Notes" - accent here Figure 1. The opening theme of Beethoven's 5th symphony. Melodic and pitch temporal accents are indicated by the letters "M" and "T", respectively. inter-accent period. We hypothesize that a complex JAS will hinder a listener's ability to monitor, and hence time(ms) anticipate, the trajectory of a melodic event. This might be evident in listeners' responses to accents as they occur. To test this hypothesis, we constructed two sets of music-like 2b: Magnitude of Pitch Skips patterns that differed in JAS temporal coherence: concordant (simple) and discordant (complex). In both sets, melodic accents (m) were derived from contour inflec- tions, and temporal accents (t) were derived from silences pitch 'accent here (rests) in the rhythmic pattern. In Experiment one, all experimental sequences comprised melodic accents that occurred every four beats; thus, m accents have a four beat "accent period." In this experiment, the temporal accents for concordant patterns assumed a four beat accent period time(ms) whereas those for discordant patterns assumed a six beat period. The relations between periods of different accent types in concordant patterns therefore coincided (both Figure 2. Two examples of melodic accentuation, using a pitch space vs. four-beat periods) whereas the relations between the two a time coordinate system. different accent periods in discordant patterns created a Accentuation, therefore, involves grouping, and polyrhythm. In Experiment two, melodic and temporal accentuation may operate with or against natural biases accent relationships were reversed. Our aim in these people have to group sequences in certain ways. For experiments is to examine the influence of these different instance, even when no explicit tone lengthenings or JAS's on how and how well people attentionally monitor pauses appear in a monotone sequence people tend to a sequence in real time. "hear" groups, often in sizes of two, defined by illusory lengthenings, pauses and/or heightened intensity. In BACKGROUND addition, they typically place subjective accents on the In this section, we provide background for our experimen- first element of such groups (Woodrow, 1909). More tal approach and predictions. We first consider evidence recently, other evidence suggests that binary temporal for various accentuation manipulations; next we review groupings are preferred (e.g., Drake, 1993; Dawe et al., related research on JAS. 1993,1994; Parncutt, 1994). Accents that determine some other groupings (e.g., 3 or 6), thus, may conflict with this Accents and Accent Strength bias. Our- experiments concentrate primarily on different combinations of melodic and temporal accents. They Melodic Accents. A variety of melodic accents are possible build on findings that indicate the perceptual salience of in musical events; among these are contour inflection, both types of accentuations. Traditionally, an accent has pitch skip, and tonal accentuation ([ones, 1987). Most arise been defined as an element of a larger auditory event that from a change in pitch that signals a deviation from some is "marked for consciousness" (Cooper & Meyer, 1960; p. pre-existing pitch motion. 8), i.e., it attracts attention. To this we add the stipulation First, the direction of pitch movement itself ("melodic that an accent derives from change along a dimension of contour") can produce accentuation. This accent, there- sound that deviates from the preexisting serial context. fore, results when the deviation from pitch motion Furthermore, successive accents help the listener organize involves a change in direction. For example, as a melody a melody into coherent groups of elements. rises in pitch some have maintained that listeners expect Joint Accent Structure 273 future events to continue this trajectory (within limits) Deliege (1987), using a segmentation task, found only a (Narmour, 1992a; Jones, 1976; 1990); in other cases, modest influence of contour in brief melodies. But others, expectancies are more complexly linked to higher-order using memory tasks, have demonstrated strong effects of contour patterns as in the gap-fill configuration contour on memory for even brief melodies (Dowling & (Schmuckler, 1989)'. In both, it is likely that a change in Fujitani, 1971; Dowling, 1978; Watkins, 1985). Although trajectory direction stands out perceptually as suggested in this research has not directly connected melodic contour Figure 2a; indeed, current research provides evidence for manipulations to accent structures, other work does imply the salience of contour changes as accents (Bigand, 1997; such a connection (Boltz & Jones, 1986; Jones & Ralston, Boltz, 1991; Boltz, Marshburn, Jones, & Johnson, 1985; 1991). Indeed, an empirical basis for choosing contour Huron & Royal, 1996; Jones & Boltz, 1989; Thomassen, over other melodic accents stems from Huron and Royal 1982). Most suggest that the accent falls on the "pivot" (1996). In a sample including European classical and folk note - i.e., the

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