Selective Attention in Two-Part Counterpoint

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Music PerceptionFall 2003, Vol. 21, No. 1, 3–20

© 2003 BY THE REGENTS OF THE UNIVERSITY OF CALIFORNIA

ALL RIGHTS RESERVED.

3

Address correspondence to Lynn L. Davison, Psychology Department, Claremont Gradu-ate University, 123 E. Eighth St., Claremont, CA 91311. (e-mail: [email protected])

ISSN: 0730-7829. Send requests for permission to reprint to Rights and Permissions,University of California Press, 2000 Center St., Ste. 303, Berkeley, CA 94704-1223.

Selective Attention In Two-Part Counterpoint

LY N N L . D AV I S O N

Claremont Graduate University

W I L L I A M P . B A N K S

Pomona College

In two experiments, the influence of unattended musical content on theprocessing of attended content was investigated by using melodic inter-val pairs. In Experiment 1, 2 two-note melodic fragments were playedconcurrently in separate pitch registers and with different timbres. Par-ticipants with music training were timed as they decided whether onemelody was rising or falling while ignoring the other. Pitch direction (upor down) and interval type (major second and perfect fifth) of attendedand unattended intervals were orthogonally combined. The measure ofinterference was the degree to which the unattended pattern influencedthe processing time and the accuracy of judging the attended melody.Unattended voice influence from both types of intervals was observed onthe attended voice for seconds, but not fifths, in Experiment 1. The sec-ond study replicated the first with interval pairs in overlapping pitchregisters. Influence from the unattended voice was found for both sec-onds and fifths. Participants found the selection task more difficult whenparts crossed and voices were moving in contrary motion rather than inthe same direction. Implications for the emergence of global stimulusproperties in the context of musical counterpoint are discussed. Bothexperiments showed that unattended musical content can affect process-ing of attended intervals and that pitch distance may serve to moderateselective attention.

Received February 12, 1999, accepted June 24, 2003

RESEARCH on auditory attention has traditionally been concerned almostentirely with processing of verbal events. Musical perception has rarely

been the subject of research on attention, even though musical performancesoffer the listener a rich variety of attentional tasks. Little is known abouthow attention is distributed over the voices of a composition, how melody



4 Lynn L. Davison & William P. Banks

and harmony may be attended to separately or together, or how differentvoices in counterpoint may compete for attention or combine to make asingle perceptual object. For example, a baroque fugue may be heard as anintegral musical pattern, or as a simultaneous composite of independentmelodic themes separately attended. Composers and improvising musicianspresumably know intuitively the attentional constraints on perception ofsimultaneous melodic lines and can use them to good effect. In this study,we examine attentional selection in a very simple example of counterpointin an attempt to begin to chart the effect of competing musical events onselective listening.

One possible outcome with competing voices is that the unattended voicedoes not affect processing of the attended voice. This would be a case ofearly selection, in which the unattended message is blocked before any typeof cognitive and/or perceptual processing. Some evidence suggests that un-attended information is not consciously processed in selective listening.Cherry (1953; Wood & Cowan, 1995b) found that when presented withtwo competing speech messages, listeners often could not even identify thelanguage of the unattended message. Treisman and Geffen (1967) askedparticipants to make a tapping response for target words in either ear whileattending to only one side. Results showed an 87% response rate for theattended side versus 8% for the unattended message. In a dichotomouslistening task, Deutsch (1982) presented two folk songs to listeners andfound they could not identify anything about the unattended tune.

There is, on the other hand, some evidence for late selection, which pro-poses that some degree of cognitive processing occurs for unattended infor-mation, although the nature of such processing is ill-defined. It has beenshown that semantically related material that is ignored may affect selec-tive listening for identification of target words (Lewis, 1970). In an attemptto replicate Lewis’ results however, Treisman, Squire, and Green (1974)found an effect of relevant unattended information only for words at thebeginning of a list. Other supporting evidence shows that hearing one’sname may cause a shift in attention to the irrelevant channel (Moray, 1959;Wood & Cowan, 1995a), and presentation of the target word in an ig-nored message that immediately precedes the same word in a shadowingtask may cause longer reaction times in an effect known as negative prim-ing (Banks, Roberts, & Ciranni, 1995).

In view of the preceding evidence, it is possible that early or late selec-tion may occur depending upon the set of perceptual conditions. Early se-lection predicts no interference from unattended stimuli and therefore couldapply to events that are perceptually distant (e.g., semantically unrelatedor separated in auditory space). In contrast, interference may or may notoccur with late selection if there is some degree of processing of the unat-



5Selective Attention in Counterpoint

tended information. Moreover, conditions of relatedness could underlie lateselection, and such conditions could prevent selection of a single event.

Whether competing events are perceived independently or as an integralstimulus is an important factor underlying the selective attention process.The voices of a musical composition are in fact components of a singlemusical texture and may therefore be difficult to attend to separately be-cause the interrelations between them would most likely affect processingof the unattended voice. Bregman (1990) proposed a framework to deter-mine whether multiple sounds may be grouped together and perceived as aseparate auditory stream. We use the term “auditory stream” in accor-dance with Bregman’s definition, in that it does not refer to the acousticproperties of a stimulus, but to a single perceptual unit that may includeone or more sounds. In other words, any combination of auditory eventsthat is grouped together as a single mental representation may be consid-ered a stream. It follows that the group of events included in a single streamwould be perceived holistically, or as a single object. In the present study,Bregman’s auditory scene analysis will serve as the perceptual frameworkfor examining whether unattended information affects processing of theattended voice in a set of varying musical conditions.

In this study, selective attention in the perception of two-note melodicinterval pairs was investigated by determining whether there is any influ-ence of the unattended melody on processing of the attended melody. If thetwo intervals are heard independently as separate streams, there should belittle influence or conflict between them, which also supports the early se-lection view. Alternatively, if influence from the unattended interval is ob-served on processing of the attended interval, then a global percept, orsingle auditory stream, most likely exists.

A number of factors may determine whether there is influence betweencompeting melodies and whether selection is easy or difficult. The organi-zation of tones according to pitch register may facilitate selective attentionto a single voice (Deutsch, 1982). This is an example of the Gestalt prin-ciple of proximity, in that high and low tones may be categorized sepa-rately, and once there is sufficient distance in pitch between two melodicpatterns, each voice will be perceived independently. Dowling (1973) foundthat when two well-known nursery rhymes were interleaved together (al-ternating tones from each melody) in a common pitch register the melodyof each was lost. However, at the point just beyond where pitch registersdid not overlap, listeners were able to identify the two melodies correctly,suggesting the importance of frequency groupings in melodic perception.Krumhansl and Schmuckler (1986) found that when two different tonalcenters (C and F♯) were presented simultaneously in a passage fromStravinsky’s “Petroushka,” participants were not able to distinguish the




two keys. The effect was largely attributable to the overlapping of pitchregisters, implying that the parts might have been distinguished had theybeen separated according to high- and low-frequency groupings.

In addition to varying pitch register, composers often employ differenttimbres for competing melodic parts when trying to achieve separationbetween voices. For example, the “Inchworm Song” from “Hans ChristianAnderson,” has the male lead singing “Inchworm, inchworm . . . ,” in atenor voice while the children sing a counter melody, “Two and two arefour . . . “ in a high soprano voice; the two parts being distinguished byboth frequency and timbre.

A third factor that may affect whether or not a listener will be able todistinguish concurrent musical parts is the degree to which the parts areplayed in synchrony. Rasch (1978) found that simultaneous tones with iden-tical rise times (synchronous) tend to fuse together into one tone whereas adifference of only 10 ms in the rise times of two instruments (quasi-simul-taneous) can facilitate perceptual distinction between parts. He claimedthat different rise times may be equivalent to the effect perceived with dif-ferent onset times. In a related study, Rasch (1979) claimed that most en-semble playing is not performed in perfect synchrony and that the degreeof asynchrony between instruments averages between 30 and 50 ms. In thepresent study, all stimuli were quasi-simultaneous in terms of rise timesand therefore assumed not to impede part distinction.

The preceding discussion suggests that selective attention to individualmusical parts should be easier when parts are played in separate pitch reg-isters, different timbres, and with asynchronous note onsets. Accordingly,these factors are considered in the test stimuli, as we are especially inter-ested in examining whether unattended channel influence exists in condi-tions that enable part distinction.

Pitch direction and interval type, being fundamental components ofmelodic perception, were chosen for the present study as variables withwhich to examine interference in selective processing of melodic voices.Intervallic identification is not the focus here, but rather the ability to de-termine in which direction an interval is moving in the presence of a com-peting interval. But more important, the interval combinations provide abasis for studying differences in selection for melodies moving in the samedirection versus contrary motion, which is an important aspect of counter-point.

The main point of Experiment 1 is to investigate whether under certainconditions of separation there would still be some level of unattended mu-sical processing. Ten participants were asked to determine whether an in-terval was moving up or down in pitch while a second interval was pre-sented simultaneously. In this experiment, two quasi-simultaneous intervalswere differentiated by timbre and played together several octaves apart.




The five independent variables were pitch direction for the attended voice(up versus down), interval type for the attended voice (major second versusperfect fifth), pitch direction for the unattended voice, interval type for theunattended voice, and instrument timbre (piano versus bassoon) in a within-subjects design. The piano timbre was used for the high intervals and thebassoon timbre for the low intervals in all conditions. Reaction time andaccuracy were measured to assess the effect of the unattended interval onprocessing of the attended interval.

If selective attention is effective, in the sense of creating effective earlyselection, then no variation in performance on the attended interval shouldbe observed as a function of pitch direction or interval type. This outcomewould suggest that the intervals were able to be heard as separate auditorystreams. However, it is predicted that some level of global perception willbe present, and to the extent that selection fails, the unattended voice shouldaffect processing of the attended voice for both interval types.

Experiment 1

METHOD

Participants

One group of 10 participants was assigned to eight blocks of 32 treatment conditionsthat were presented in random order. Participants had a range of 3 to 12 years of musictraining and were all professional, performing musicians. Eight males and two females weretested. Ages were from 19 to 49 years old.

Design

A 2 × 2 × 2 × 2 × 2 within-subjects design was used to study whether unattended channelinformation may affect performance in a selective listening task with competing melodicintervals in various stimulus conditions. The five independent variables were attended di-rection (up versus down), attended interval type (perfect fifth versus major second), unat-tended direction, unattended interval type, and timbre (piano versus bassoon). The depen-dent variables were reaction time and accuracy.

Procedure

A Macintosh Power PC was used to run a Superlab program with 16 sound stimulirecorded on an Ensoniq TS10 synthesizer that were played into the computer with soundediting software. Each stimulus consisted of two intervals played simultaneously, with thehigher voice on piano and the lower voice in a bassoon-like timbre. Stimuli ranged in sepa-ration from one and a half to three octaves. Both timbres were sampled waveforms of realinstruments. The onset tones of all interval pairs were quantized so that they began at thesame time, but the difference in rise times caused the bassoon timbre to peak 13 ms laterthan the piano, which is more indicative of real musical performance than perfect synchro-nous onset (Rasch, 1978). Release times varied within 25 ms as a function of performance.Sounds were recorded monophonically, and both ears received the same signal through




headphones. The levels of the two timbres were electronically equalized and then adjustedmanually so that they sounded equal in volume.

Stimuli included a perfect fifth or major second moving up or down, against a perfect fifthor major second moving up or down, in upper and lower voices (see Figure 1). It should benoted that the vertical intervals created between the two onset and offset notes of the intervalpairs were not systematically varied in the study, but categorized in terms of consonant ordissonant combinations to address the possibility of an effect. Each stimulus contained twovertical intervals. Consonant conditions included 12 stimuli with perfect fourths or fifths and4 stimuli with one perfect fourth or fifth and one minor third, whereas dissonant combinationsincluded 16 stimuli with one perfect fourth or fifth and one major second or minor seventh. Itshould be noted that the small number of stimuli that contained the minor thirds were in-cluded in the consonance category, as they are closer to consonance than dissonance, but mayactually be described more accurately as imperfect consonance.

All tones belonged to the C-major scale and the intervals were played legato. The firsttone lasted 500 ms, and the second tone was allowed to gradually decay for 2 s. The firsttone was immediately followed by the second with no silence in between. In some trials, thedecay of the second tone was cut short by the participant’s response, which triggered thenext interval presentation.

Half the participants were asked to listen to the piano voice and determine whether itwas moving up or down, while ignoring the bassoon, whereas the other half listened to thebassoon voice first while ignoring the piano. Each group was then instructed to switch theirattention to the unattended timbre for the last half of the trials. Sixteen interval combina-tions were presented eight times each in 128 trials for each timbre, totaling 256 trials.Participants indicated their responses by pressing u (up) or d (down), with each responsecueing up the next trial. A 9-s time limit was set for each. All errors were tabulated for eachcondition, but reaction times were tabulated only for trials answered correctly.

Fig. 1. All test stimuli used in Experiment 1. Sixteen pairs of two-note melodies comprisingascending and descending major second and perfect fifth intervals in separate pitch registers.


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RESULTS

The data were analyzed in a five-variable analysis of variance (ANOVA),with variables of attended direction (up versus down), unattended direc-tion (up versus down), attended interval type (perfect fifth versus majorsecond), unattended interval type (perfect fifth versus major second), andtimbre (piano versus bassoon). Main effects and interactions not explicitlydescribed were not significant (p > .05).

Results of an ANOVA of reaction time showed evidence of a three-wayinteraction between attended direction, unattended direction, and attendedinterval type, F(1,9) = 8.19, p = .019, MSE = 81519.50. A follow-upANOVA showed an interaction between attended and unattended inter-vals for major seconds, F(1,9) = 24.82, p < .001, MSE = 81519.50, but notperfect fifths. A plot of mean reaction times for the major seconds showingattended versus unattended direction (see Figure 2) revealed a crossoverpattern such that the attended “up” condition was processed faster whenthe unattended interval was “up” (1712 ms) than when it was “down,” (1821ms) and the attended “down” condition was processed faster when the unat-tended interval was “down” (1548 ms) than when it was “up” (1664 ms). Inother words, listeners took longer to respond when melodies were moving incontrary motion rather than in the same direction for major seconds.

A main effect of attended direction was also observed for major secondsF(1,9) = 50.56, p < .001, MSE = 81519.50. Means showed that reaction

Fig. 2. Reaction time to judge melodic direction of attended interval for major seconds(excluding unattended fifths) in Experiment 1. Reaction time is faster when both attendedand unattended intervals are moving in the same direction than when they are in contrarymotion.

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time was faster when the attended interval moved down (1606 ms) thanwhen it moved up (1766 ms) regardless of the direction of the unattendedinterval.

In contrast to the results for major seconds, there was no significantinteraction between attended and unattended intervals for perfect fifths (p> .05). The pattern of mean reaction times, however, shows that processingtook the least amount of time when the attended voice moved down andthe unattended voice moved up (1564 ms), followed by when both voicesmoved up (1581 ms), then when the attended voice moved up and theunattended voice moved down (1620 ms), and finally when both voicesmoved down (1744 ms), which took longest (see Figure 3).

There were significant two-way interactions between attended intervaltype and attended direction, F(1,9) = 22.01, p < .001, MSE = 41688.51,and between attended interval type and unattended direction, F(1,9) = 6.48,p = .031, MSE = 39234.42.

Timbre was not significant (p > .05). Mean reaction times were similarfor piano (1653 ms) and bassoon (1660 ms).

In addition, mean reaction times were tabulated for the vertical intervalscreated between interval pairs. Results were similar for consonant (1683ms) versus dissonant (1657 ms) combinations.

A within-subjects ANOVA measuring accuracy showed no significanteffects (p > .05). According to Figure 4, the pattern of means showed a

Fig. 3. Reaction time to judge melodic direction of attended interval for perfect fifths (ex-cluding unattended seconds) in Experiment 1. Differences were not significant.

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slightly higher accuracy rate when both the attended and unattended inter-vals moved down (99%), and when the attended interval moved downwhile the unattended interval moved up (98%), compared with when bothintervals moved up (97%), and when the attended interval moved up whilethe unattended interval moved down (96%). Mean accuracy rates weresimilar for piano (98%) and bassoon (97%).

DISCUSSION

These results support an effect of stimulus competition on listeners’ abil-ity to determine pitch contour when major second intervals were used inthe attended voice. The perfect fifth intervals did not incur significant per-formance differences. Because the effect was observed in small interval con-ditions only, we could conclude that the major second interval may be morevulnerable to input from the unattended information than the perfect fifth.

Given that reaction time was affected and not accuracy, it could be that thelistener hesitated because traditional musical expectancies were not met whenthe major second intervals were presented in comparison to the consonantfifths. It is known that a perfect fifth is more harmonically stable than a majorsecond (Krumhansl, 1990). Thus, the two tones comprising a perfect fifthcould provide an interval more resistant to interference than the major second.The hierarchy of tonal organization is such that the tonic, fifth, and third aremost stable, in that the listener can predict harmonic resolution. Although

Fig. 4. Accuracy rate to judge melodic direction of attended interval for major seconds andperfect fifth intervals (averaged across unattended seconds and fifths) in Experiment 1.Differences were not significant.

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listeners required more time to process the major seconds than the perfectfifths, they were in fact able to distinguish the high and low intervals as sepa-rate auditory streams, as reflected in the high degree of accuracy.

The intervals in the first experiment were separated by both pitch regis-ter and timbre, both of which are known to facilitate discrimination(Deutsch, 1982; Dowling, 1973; Krumhansl, 1990). Therefore, any inter-ference observed under these conditions would indicate a fairly robust ef-fect. In Experiment 2, the same intervals (major seconds and perfect fifths)were transposed into a common octave. With intervals in the same register,only timbral differences and a small degree of asynchrony due to the differ-ence in rise times serve to distinguish the two melodic sequences, and sodiscrimination should be more difficult than in Experiment 1. Moreover,global stimulus properties are expected to be more prominent in Experiment 2than in Experiment 1, as merging the intervals into a common pitch registermay increase the relatedness between attended and unattended voices.

One factor underlying musical relatedness is the perceptual relation betweenmelodic and harmonic groupings, which are inherently formed within the stimu-lus configuration of concurrent voices. Perception of one or the other may beemphasized depending upon the distance between voices, and the relative bal-ance between the two may be altered accordingly. Perception of the horizontaldimension, which is analogous to the melodic aspect, will become strongerwith the degree of distance between the two melodies, whereas the verticaldimension, which is analogous to the harmonic component, will systemati-cally weaken (Bregman, 1990). Thus, perception of the harmonic dimensionshould become more prominent in Experiment 2 than in Experiment 1, and agreater degree of perceptual fusion between voices is likely to occur. There isalso a greater likelihood that the vertical intervals formed by the interval pairscould have an effect as compared with the first experiment.

If the relatedness between voices is increased as a function of proximity,then listeners should have difficulty determining which line to follow, andaccuracy rates should be lower than they were in Experiment 1. We might alsoexpect an influence on processing the perfect fifth interval that was not seen inExperiment 1, as global processing would most likely affect melodic percep-tion of both interval types. Furthermore, there may be differences with melo-dies that are moving in the same direction versus contrary motion.

Experiment 2

METHOD

Participants

One group of 10 participants was assigned to eight blocks of 32 treatment conditionsthat were presented in random order as in Experiment 1. Participants had a range of be-




tween 3 and 15 years of music training and were all professional, performing musicians. Sixmales and four females were tested. Participants were from 23 to 46 years old.

Design

A 2 x 2 x 2 x 2 x 2 within-subjects design was used with the same independent variablesas in Experiment 1, which included attended pitch direction (up versus down), attendedinterval type (major second versus perfect fifth), unattended direction, unattended intervaltype, and timbre (piano versus bassoon). The dependent variables were reaction time andaccuracy.

Procedure

The same procedure was used in Experiment 2 as in Experiment 1, except that the inter-vals were placed in the same pitch register rather than separated into high- and low-fre-quency ranges. Part-crossing took place in 6 of the 16 interval combinations, but two notesplayed at the same time were never overlapping in pitch. It should be noted, however, thatpart-crossing always occurred with interval pairs that were moving in contrary motion.Also, an interstimulus interval of 500 ms was added to the beginning of the next trial so thatbefore each response there would be a brief preparation period. The rest interval was trig-gered by the participant’s response to the previous trial and was deducted from reactiontime scores, so that the results could be compared with those of Experiment 1. The degreeof asynchrony for onset notes was held constant between the two experiments. Participantswere presented with interval pairs and asked to listen to the piano or bassoon voice todetermine whether the attended voice was moving up or down. Once again, reaction timesfor correct trials and errors were tabulated for each condition.

RESULTS AND DISCUSSION

As in Experiment 1, the data were analyzed in a five-variable ANOVA,with variables of attended direction (up versus down), unattended direc-tion (up versus down), attended interval type (perfect fifth versus majorsecond), unattended interval type (perfect fifth versus major second), andtimbre (piano versus bassoon). Main effects and interactions not explicitlydescribed were not significant (p > .05).

Results from an ANOVA of reaction time showed an overall two-wayinteraction between attended and unattended pitch direction, F(1,9) = 7.31,p = .043, MSE = 124897.70. A follow-up ANOVA that measured perfectfifths versus major seconds showed no significant interaction for attendedx unattended direction (p > .05) for either interval type.

Some support for the facilitation of selective attention in congruent ver-sus incongruent conditions was observed. Mean performance across allconditions showed a crossover interaction (see Figure 5), with the bestperformance having been observed when the attended and unattended in-tervals both moved down (2119 ms). However, results were the same forconditions in which both intervals moved up (2191 ms) and conditions inwhich the attended interval moved up while the unattended interval moveddown (2191 ms). The longest reaction times were observed when the at-tended interval moved down while the unattended voice moved up (2277ms).




Means showed that crossing intervals (2252 ms) took longer to processthan noncrossing intervals (2138 ms). Interval pairs moving in contrarymotion that actually crossed took longer to process (2252 ms) than didnoncrossing incongruent intervals (2123 ms). There was little difference inreaction time between noncrossing incongruent conditions (2123 ms) andconditions in which intervals moved in the same direction (2152 ms). Itshould be noted that of the 32 interval pairs, 12 crossed and 20 did not,with 16 of the latter being congruent and 4 pairs moving in contrary mo-tion.

There was a highly significant main effect of unattended interval type,F(1,9) = 86.20, p < .001, MSE = 12338.94, and also an effect of unat-tended direction, F(1,9)=15.53, p = .011, MSE = 33638.89 on reactiontime for the attended interval.

Timbre was not significant (p > .05). Mean reaction times were similarfor piano (2685 ms) and bassoon (2701 ms).

Mean reaction times for vertical interval combinations were similar, withperformance for consonant intervals at 2695 ms and dissonant intervals at2656 ms. The vertical intervals were categorized in the same manner as thestimuli in Experiment 1.

Results from an ANOVA of accuracy showed a highly reliable two-wayinteraction between attended and unattended direction, F(1,9) = 147.53, p

Fig. 5. Reaction time to judge melodic direction of attended interval for major seconds andperfect fifth intervals (averaged across unattended seconds and fifths) in Experiment 2.Reaction time is faster when both intervals are moving in the same direction than when theyare in contrary motion.

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< .001, MSE = 433.11. The overall pattern was the same for accuracy asfor reaction time. Accuracy rates (see Figure 6) were highest when bothintervals moved down (96%), followed by congruent “up” conditions(89%). The second lowest scores were observed in conditions in which theattended voice moved up and the unattended voice moved down (69%),whereas the most errors occurred when the attended voice moved downand the unattended voice moved up (59%).

Selective attention was easier when the intervals moved in the same di-rection rather than in contrary motion. Congruent conditions showed amean accuracy rate of 92% in contrast to the 64% accuracy rate observedin combined incongruent conditions, some of which included part-cross-ing.

Mean accuracy rates were 62% for crossing parts and 88% fornoncrossing parts (see Figure 7). Incongruent interval pairs that crossedproduced the lowest accuracy rate (62%), followed by noncrossing incon-gruent intervals (70%), with melodies moving in the same direction show-ing the highest accuracy rate (92%).

Other significant interactions included a two-way interaction betweenattended interval type and attended direction, F(1,9) = 12.98, p < .006,MSE = 438.01; a three-way interaction between attended direction, unat-

Fig. 6. Accuracy rate to judge melodic direction of attended interval for major seconds andperfect fifth intervals (averaged across unattended seconds and fifths) in Experiment 2.Accuracy rate is higher when both intervals are moving in the same direction than whenthey are in contrary motion.

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tended direction, and unattended interval type, F(1,9) = 12.16, p = .007,MSE = 197.71; and a four-way interaction between attended direction,unattended direction, attended interval type, and unattended interval type,F(1,9) = 38.45, p < .001, MSE = 51.89. Main effects were significant forunattended direction, F(1,9) = 8.42, p = .018, MSE = 779.76, and unat-tended interval type, F(1,9) = 8.08, p = .019, MSE = 314.63.

Timbre had a significant effect on performance accuracy, F(1,9) = 5.56,p = .043, MSE = 946.29. Means showed that the identification of pitchdirection was more accurate when the attended voice was in a bassoon(82%) rather than a piano timbre (74%). In addition, a significant three-way interaction was observed for instrument x attended direction x unat-tended direction, F(1,9) = 5.54, p = .043, MSE = 588.65, as well as signifi-cant two-way interactions for instrument x attended direction, F(1,9) =6.96, p = .027, MSE = 674.89, and instrument x unattended direction,F(1,9) = 6.11, p = .035, MSE = 216.90.

Mean accuracy rates for vertical interval combinations were almost thesame, with consonant intervals being processed at a mean accuracy rate of76% and dissonant intervals at 77%.

The pattern of means offers strong evidence that unattended melodicpatterns can affect processing of attended ones. In Experiment 2, interfer-ence was observed for both accuracy and reaction time, whereas in Experi-ment 1, an effect was seen for reaction time but not accuracy. A compari-

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Fig. 7. Accuracy rates for crossing versus noncrossing interval pairs in Experiment 2.




son of the two experiments for both errors and reaction times suggests thatplacing the intervals in a common pitch register made the task more diffi-cult. Overall mean accuracy rates showed a 20% decrease from the firstexperiment to the second, with 98% for Experiment 1 and 78% for Ex-periment 2. A comparison of reaction times showed a mean difference of536 ms between Experiment 1 (1657 ms) and Experiment 2 (2193 ms).However, it is possible that having no interstimulus interval between theresponse and the next trial could have caused listeners to feel rushed inExperiment 1, which may have contributed to the difference in reactiontime.

The bassoon timbre advantage observed in Experiment 2 with accuracymay be attributable to some degree of backward masking of the pianovoice as a result of the 13-ms difference in rise times (Rasch, 1978), whichcould be less prominent in conditions of interval separation.

General Discussion

These findings show that unattended musical parts of a compositionmay strongly affect processing of an attended voice and that the degree ofinterference may vary according to compositional factors that determinehow musical attributes are interrelated. In both experiments, there wasinfluence of the unattended interval on the attended one, and this was in-creased in the second experiment in which pitch registers were overlap-ping. Given that early selection assumes that no processing occurs withunattended stimuli, it could not have been possible in conditions that showedan effect of the unattended voice on processing of the attended voice. Alter-natively, late selection implies that some processing of unattended informa-tion occurred, but does not distinguish the nature or degree of such pro-cessing. It is possible that conditions of relatedness between competing voicesmay serve to mediate unattended voice processing, which could be due tothe emergence of global stimulus properties.

It has been argued that when events are perceptually independent, selec-tive attention is facilitated, whereas in global perception, a set of elementsis perceived as a unit and selection of individual elements may be impaired(Banks & Prinzmetal, 1979; Bonnel & Prinzmetal, 1998; Prinzmetal &Banks, 1977). The extremely high accuracy rates reported in Experiment 1indicated that listeners could perceive the two melodies independently,whereas in Experiment 2, the sharp decline in accuracy rates showed thatlisteners could not identify parts in the same pitch register, suggesting theyprobably heard a single auditory stream. Presumably, a group of soundsthat are grouped together as an auditory stream would be perceived as aglobal entity.




It also appears that when voices crossed, the melodies became even moredifficult to distinguish than when voices moving in contrary motion didnot cross, which is important in the context of musical counterpoint. In aseries of studies that examined the structure of counterpoint, Huron (1991)found that J. S. Bach avoided part-crossing, especially when three or morevoices were being played simultaneously, suggesting that overlapping melo-dies may be difficult to attend to even when they are played in differenttimbres and that counterpoint voices written in separate pitch registers mayfacilitate melodic independence.

The difficulty in attending to individual voices moving in contrary mo-tion may be understood in the context of the Gestalt principle of commonfate. When two concurrent voices are moving in the same direction, thestimulus as a whole is either moving up or down, in which case the task ofdetermining the direction of the attended voices should be easier becausethe melodies are moving congruently. In contrast, when voices are heard incontrary motion, an up or down judgment for a selected voice should bemore difficult because the listener is subjected to conflicting information. Itis important to note that if the voices are heard independently, then con-gruence of movement should not have any effect. For the most part how-ever, attentional performance was slower and less accurate when voiceswere moving in contrary motion rather than in the same direction, suggest-ing some degree of global perception.

Whether concurrent musical voices are perceived independently or as acoordinated musical texture may be affected by the relative prominence ofmelodic and harmonic dimensions. As discussed previously, the verticaldimension becomes more prominent with proximity, in that individual tonesfrom concurrent melodies are more likely to be perceived as a harmonicgrouping when they are close together rather than separated in auditoryspace (Bregman, 1990). Conversely, the horizontal dimension (melody) maybe perceptually dominant over the harmonic structure as a result of melo-dies being in separate registers, thereby establishing perceptual indepen-dence between voices.

The inherent compositional structure of counterpoint appears to havedual implications for selective attention ability, in that individual voicesmay be perceived as both independent and integral. So rather than try toclassify a set of polyphonic voices as being absolutely integral or indepen-dent, it may be more reasonable to try and define the conditions underwhich competing voices may be perceived separately, or as an integralmusical texture. Moreover, because individual parts of a composition arewritten to be perceived as a cohesive whole, there should exist some degreeof global perception regardless of how distinguishable individual musicalmotifs may be to the listener. Therefore, attentional interference from com-peting musical attributes in the context of integrality may be intended to




some degree by the composer as part of the perceptual experience. In poly-phonic composition, the issue of global perception becomes even more com-plex, as the ability to maintain melodic independence becomes more diffi-cult with an increased number of voices (Huron, 1989).

There are certain factors to consider when attempting to generalize thefindings of the present study to normal listening. First, listeners were in-structed to follow one voice and ignore the other, thus placing constraintson voluntary processes that would otherwise not exist in normal listening.Second, a higher degree of asynchrony in note onsets would be expectedbetween performing acoustic instruments as compared with synthesizedrecorded instruments, although even a slight deviation from synchrony mayserve to facilitate distinction between parts (Rasch, 1979). The intervalpairs in the present study were asynchronous in that they consisted of tim-bres with different rise times, and so it is unlikely that the interferenceobserved in this study was due to synchrony of onset. And further, it couldnot explain differences between experiments, as the timing of onset for allstimuli was held constant between experiments. And finally, the melodiespresented in real music are typically much longer than the two-note inter-vals presented here, and as such, may affect the creation of musical expect-ancies that result in each melodic fragment priming the next.

In conclusion, these results suggest an attentional basis for rules of com-position seen in counterpoint, which serves to promote a masterful balancebetween individual part distinction and the perception of concurrent voicesas a global texture based on interrelations between musical attributes.

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Selective Attention in Two-Part Counterpoint

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