Vibrotactile enhancement of musical engagement.

Sound is sensed by the ear but can also be felt on the skin, by means of vibrotactile stimulation. Only little research has addressed perceptual implications of vibrotactile stimulation in the realm of music. Here, we studied which perceptual dimensions of music listening are affected by vibrotactile stimulation and whether the spatial segregation of vibrations improves vibrotactile stimulation. Forty-one listeners were presented with vibrotactile stimuli via a chair's surfaces (left and right arm rests, back rest, seat) in addition to music presented over headphones. Vibrations for each surface were derived from individual tracks of the music (multi condition) or conjointly by a mono-rendering, in addition to incongruent and headphones-only conditions. Listeners evaluated unknown music from popular genres according to valence, arousal, groove, the feeling of being part of a live performance, the feeling of being part of the music, and liking. Results indicated that the multi- and mono vibration conditions robustly enhanced the nature of the musical experience compared to listening via headphones alone. Vibrotactile enhancement was strong in the latent dimension of 'musical engagement', encompassing the sense of being a part of the music, arousal, and groove. These findings highlight the potential of vibrotactile cues for creating intensive musical experiences.

Development of an adaptive test of musical scene analysis abilities for normal-hearing and hearing-impaired listeners.

Auditory scene analysis (ASA) is the process through which the auditory system makes sense of complex acoustic environments by organising sound mixtures into meaningful events and streams. Although music psychology has acknowledged the fundamental role of ASA in shaping music perception, no efficient test to quantify listeners' ASA abilities in realistic musical scenarios has yet been published. This study presents a new tool for testing ASA abilities in the context of music, suitable for both normal-hearing (NH) and hearing-impaired (HI) individuals: the adaptive Musical Scene Analysis (MSA) test. The test uses a simple 'yes-no' task paradigm to determine whether the sound from a single target instrument is heard in a mixture of popular music. During the online calibration phase, 525 NH and 131 HI listeners were recruited. The level ratio between the target instrument and the mixture, choice of target instrument, and number of instruments in the mixture were found to be important factors affecting item difficulty, whereas the influence of the stereo width (induced by inter-aural level differences) only had a minor effect. Based on a Bayesian logistic mixed-effects model, an adaptive version of the MSA test was developed. In a subsequent validation experiment with 74 listeners (20 HI), MSA scores showed acceptable test-retest reliability and moderate correlations with other music-related tests, pure-tone-average audiograms, age, musical sophistication, and working memory capacities. The MSA test is a user-friendly and efficient open-source tool for evaluating musical ASA abilities and is suitable for profiling the effects of hearing impairment on music perception.

Exploring level- and spectrum-based music mixing transforms for hearing-impaired listeners.

Multitrack mixing is an essential practice in modern music production. Research on automatic-mixing paradigms, however, has mostly tested samples of trained, normal hearing (NH) participants. The goal of the present study was to explore mixing paradigms for hearing-impaired (HI) listeners. In two experiments, the mixing preferences of NH and HI listeners with respect to the parameters of lead-to-accompaniment level ratio (LAR) and the low to high frequency spectral energy balance were investigated. Furthermore, preferences of transformed equalization (EQ-transform) were assessed, achieved by linearly extrapolating between the power spectrum of individual tracks and a reference spectrum. Multitrack excerpts of popular music were used as stimuli. Results from experiment 1 indicate that HI participants preferred an elevated LAR compared to NH participants but did not suggest distinct preferences regarding spectral balancing or EQ-transform. Results from experiment 2 showed that bilateral hearing aid (HA) disuse among the HI participants yielded higher LAR values, stronger weighting of higher frequencies, as well as sparser EQ-transform settings compared to a condition with HA use. Overall, these results suggest that adjusting multitrack mixes may be a valuable way for making music more accessible for HI listeners.

Lead-vocal level in recordings of popular music 1946-2020.

Lead vocals constitute the central element of popular music. Here, the lead-vocal-to-accompaniment level ratio (LAR) was estimated from representative recordings of popular music. Measuring the LAR from 1946 to 2020, two distinct phases were observed: the average LAR decreased from around 5 dB to 1 dB until around 1975 but remained static from thereon. Comparing the LAR across musical genres, positive values were observed for Country, Rap, and Pop, values around zero for Rock, and negative values for Metal. Solo artists featured consistently higher LAR values compared to bands. These results establish a baseline for a central aspect of music mixing.

A unitary model of auditory frequency change perception.

Changes in the frequency content of sounds over time are arguably the most basic form of information about the behavior of sound-emitting objects. In perceptual studies, such changes have mostly been investigated separately, as aspects of either pitch or timbre. Here, we propose a unitary account of "up" and "down" subjective judgments of frequency change, based on a model combining auditory correlates of acoustic cues in a sound-specific and listener-specific manner. To do so, we introduce a generalized version of so-called Shepard tones, allowing symmetric manipulations of spectral information on a fine scale, usually associated to pitch (spectral fine structure, SFS), and on a coarse scale, usually associated timbre (spectral envelope, SE). In a series of behavioral experiments, listeners reported "up" or "down" shifts across pairs of generalized Shepard tones that differed in SFS, in SE, or in both. We observed the classic properties of Shepard tones for either SFS or SE shifts: subjective judgements followed the smallest log-frequency change direction, with cases of ambiguity and circularity. Interestingly, when both SFS and SE changes were applied concurrently (synergistically or antagonistically), we observed a trade-off between cues. Listeners were encouraged to report when they perceived "both" directions of change concurrently, but this rarely happened, suggesting a unitary percept. A computational model could accurately fit the behavioral data by combining different cues reflecting frequency changes after auditory filtering. The model revealed that cue weighting depended on the nature of the sound. When presented with harmonic sounds, listeners put more weight on SFS-related cues, whereas inharmonic sounds led to more weight on SE-related cues. Moreover, these stimulus-based factors were modulated by inter-individual differences, revealing variability across listeners in the detailed recipe for "up" and "down" judgments. We argue that frequency changes are tracked perceptually via the adaptive combination of a diverse set of cues, in a manner that is in fact similar to the derivation of other basic auditory dimensions such as spatial location.

Adaptive auditory brightness perception.

Perception adapts to the properties of prior stimulation, as illustrated by phenomena such as visual color constancy or speech context effects. In the auditory domain, only little is known about adaptive processes when it comes to the attribute of auditory brightness. Here, we report an experiment that tests whether listeners adapt to spectral colorations imposed on naturalistic music and speech excerpts. Our results indicate consistent contrastive adaptation of auditory brightness judgments on a trial-by-trial basis. The pattern of results suggests that these effects tend to grow with an increase in the duration of the adaptor context but level off after around 8 trials of 2 s duration. A simple model of the response criterion yields a correlation of r = .97 with the measured data and corroborates the notion that brightness perception adapts on timescales that fall in the range of auditory short-term memory. Effects turn out to be similar for spectral filtering based on linear spectral filter slopes and filtering based on a measured transfer function from a commercially available hearing device. Overall, our findings demonstrate the adaptivity of auditory brightness perception under realistic acoustical conditions.

Spectral envelope position and shape in sustained musical instrument sounds.

It has been argued that the relative position of spectral envelopes along the frequency axis serves as a cue for musical instrument size (e.g., violin vs viola) and that the shape of the spectral envelope encodes family identity (violin vs flute). It is further known that fundamental frequency (F0), F0-register for specific instruments, and dynamic level strongly affect spectral properties of acoustical instrument sounds. However, the associations between these factors have not been rigorously quantified for a representative set of musical instruments. Here, we analyzed 5640 sounds from 50 sustained orchestral instruments sampled across their entire range of F0s at three dynamic levels. Regression of spectral centroid (SC) values that index envelope position indicated that smaller instruments possessed higher SC values for a majority of instrument classes (families), but SC also correlated with F0 and was strongly and consistently affected by the dynamic level. Instrument classification using relatively low-dimensional cepstral audio descriptors allowed for discrimination between instrument classes with accuracies beyond 80%. Envelope shape became much less indicative of instrument class whenever the classification problem involved generalization to different dynamic levels or F0-registers. These analyses confirm that spectral envelopes encode information about instrument size and family identity and highlight their dependence on F0(-register) and dynamic level.

Repetition and Aesthetic Judgment in Post-tonal Music for Large Ensemble and Orchestra.

Post-tonal music often poses perceptual and cognitive challenges for listeners, potentially related to the use of relatively uncommon and unfamiliar musical material and compositional processes. As a basic compositional device, repetition affects memory for music and is structured by composers in very different ways across tonal and post-tonal musical repertoires. Of particular concern is whether post-tonal music exhibits mnemonic affordances that allow listeners to experience a sense of global coherence, and whether repetition correlates strongly with aesthetic judgment. Although previous research suggests that repetition impacts aesthetic preference, empirical research has not mapped out the relationship between repetition and aesthetic judgments across a broad set of post-tonal music. Presenting 14 excerpts, grouped into three categories: tonal, modernist, and post-1970, we observed that indications of repetitions in the music for a group of 60 listeners, with and without musical training, showed significant periods of interindividual synchronization. Aesthetic judgments were assessed by means of ratings for the following parameters: familiarity with the piece, confidence of repetition responses, judgments of affordances for easy listening, coherence, similarity of moments, and recognition, as well as listeners' liking and interest. A principal component analysis (PCA) on the joint question data and the repetition responses suggested that two factors account for 92% of variance in the data. These factors were interpreted as dominated by aesthetic judgment and repetition strength. Linear mixed-effects regression indicated that repetition strength generally differed across excerpt category, with modernist excerpts featuring lower repetition strength compared to both post-1970 and tonal excerpts. Aesthetic preference, on the other hand, was lower for excerpts in both the modernist and post-1970 categories when compared to tonal excerpts. The analysis did not reveal difference in response behavior for repetition responses as a function of musical training, though it indicated higher preference of modernist excerpts with increasing levels of musical training. Overall, the results suggest that the two factors, aesthetic judgment and repetition strength, act as independent determinants in the experience of post-tonal music.

Tracking Musical Voices in Bach's The Art of the Fugue: Timbral Heterogeneity Differentially Affects Younger Normal-Hearing Listeners and Older Hearing-Aid Users.

Auditory scene analysis is an elementary aspect of music perception, yet only little research has scrutinized auditory scene analysis under realistic musical conditions with diverse samples of listeners. This study probed the ability of younger normal-hearing listeners and older hearing-aid users in tracking individual musical voices or lines in JS Bach's The Art of the Fugue. Five-second excerpts with homogeneous or heterogenous instrumentation of 2-4 musical voices were presented from spatially separated loudspeakers and preceded by a short cue for signaling the target voice. Listeners tracked the cued voice and detected whether an amplitude modulation was imposed on the cued voice or a distractor voice. Results indicated superior performance of young normal-hearing listeners compared to older hearing-aid users. Performance was generally better in conditions with fewer voices. For young normal-hearing listeners, there was interaction between the number of voices and the instrumentation: performance degraded less drastically with an increase in the number of voices for timbrally heterogeneous mixtures compared to homogeneous mixtures. Older hearing-aid users generally showed smaller effects of the number of voices and instrumentation, but no interaction between the two factors. Moreover, tracking performance of older hearing aid users did not differ when these participants did or did not wear hearing aids. These results shed light on the role of timbral differentiation in musical scene analysis and suggest reduced musical scene analysis abilities of older hearing-impaired listeners in a realistic musical scenario.

Listening in the Mix: Lead Vocals Robustly Attract Auditory Attention in Popular Music.

Listeners can attend to and track instruments or singing voices in complex musical mixtures, even though the acoustical energy of sounds from individual instruments may overlap in time and frequency. In popular music, lead vocals are often accompanied by sound mixtures from a variety of instruments, such as drums, bass, keyboards, and guitars. However, little is known about how the perceptual organization of such musical scenes is affected by selective attention, and which acoustic features play the most important role. To investigate these questions, we explored the role of auditory attention in a realistic musical scenario. We conducted three online experiments in which participants detected single cued instruments or voices in multi-track musical mixtures. Stimuli consisted of 2-s multi-track excerpts of popular music. In one condition, the target cue preceded the mixture, allowing listeners to selectively attend to the target. In another condition, the target was presented after the mixture, requiring a more "global" mode of listening. Performance differences between these two conditions were interpreted as effects of selective attention. In Experiment 1, results showed that detection performance was generally dependent on the target's instrument category, but listeners were more accurate when the target was presented prior to the mixture rather than the opposite. Lead vocals appeared to be nearly unaffected by this change in presentation order and achieved the highest accuracy compared with the other instruments, which suggested a particular salience of vocal signals in musical mixtures. In Experiment 2, filtering was used to avoid potential spectral masking of target sounds. Although detection accuracy increased for all instruments, a similar pattern of results was observed regarding the instrument-specific differences between presentation orders. In Experiment 3, adjusting the sound level differences between the targets reduced the effect of presentation order, but did not affect the differences between instruments. While both acoustic manipulations facilitated the detection of targets, vocal signals remained particularly salient, which suggest that the manipulated features did not contribute to vocal salience. These findings demonstrate that lead vocals serve as robust attractor points of auditory attention regardless of the manipulation of low-level acoustical cues.

Brightness perception for musical instrument sounds: Relation to timbre dissimilarity and source-cause categories.

Timbre dissimilarity of orchestral sounds is well-known to be multidimensional, with attack time and spectral centroid representing its two most robust acoustical correlates. The centroid dimension is traditionally considered as reflecting timbral brightness. However, the question of whether multiple continuous acoustical and/or categorical cues influence brightness perception has not been addressed comprehensively. A triangulation approach was used to examine the dimensionality of timbral brightness, its robustness across different psychoacoustical contexts, and relation to perception of the sounds' source-cause. Listeners compared 14 acoustic instrument sounds in three distinct tasks that collected general dissimilarity, brightness dissimilarity, and direct multi-stimulus brightness ratings. Results confirmed that brightness is a robust unitary auditory dimension, with direct ratings recovering the centroid dimension of general dissimilarity. When a two-dimensional space of brightness dissimilarity was considered, its second dimension correlated with the attack-time dimension of general dissimilarity, which was interpreted as reflecting a potential infiltration of the latter into brightness dissimilarity. Dissimilarity data were further modeled using partial least-squares regression with audio descriptors as predictors. Adding predictors derived from instrument family and the type of resonator and excitation did not improve the model fit, indicating that brightness perception is underpinned primarily by acoustical rather than source-cause cues.

Can You Hear Out the Melody? Testing Musical Scene Perception in Young Normal-Hearing and Older Hearing-Impaired Listeners.

It is well known that hearing loss compromises auditory scene analysis abilities, as is usually manifested in difficulties of understanding speech in noise. Remarkably little is known about auditory scene analysis of hearing-impaired (HI) listeners when it comes to musical sounds. Specifically, it is unclear to which extent HI listeners are able to hear out a melody or an instrument from a musical mixture. Here, we tested a group of younger normal-hearing (yNH) and older HI (oHI) listeners with moderate hearing loss in their ability to match short melodies and instruments presented as part of mixtures. Four-tone sequences were used in conjunction with a simple musical accompaniment that acted as a masker (cello/piano dyads or spectrally matched noise). In each trial, a signal-masker mixture was presented, followed by two different versions of the signal alone. Listeners indicated which signal version was part of the mixture. Signal versions differed either in terms of the sequential order of the pitch sequence or in terms of timbre (flute vs. trumpet). Signal-to-masker thresholds were measured by varying the signal presentation level in an adaptive two-down/one-up procedure. We observed that thresholds of oHI listeners were elevated by on average 10 dB compared with that of yNH listeners. In contrast to yNH listeners, oHI listeners did not show evidence of listening in dips of the masker. Musical training of participants was associated with a lowering of thresholds. These results may indicate detrimental effects of hearing loss on central aspects of musical scene perception.

Specifying the perceptual relevance of onset transients for musical instrument identification.

Sound onsets are commonly considered to play a privileged role in the identification of musical instruments, but the underlying acoustic features remain unclear. By using sounds resynthesized with and without rapidly varying transients (not to be confused with the onset as a whole), this study set out to specify precisely the role of transients and quasi-stationary components in the perception of musical instrument sounds. In experiment 1, listeners were trained to identify ten instruments from 250 ms sounds. In a subsequent test phase, listeners identified instruments from 64 ms segments of sounds presented with or without transient components, either taken from the onset, or from the middle portion of the sounds. The omission of transient components at the onset impaired overall identification accuracy only by 6%, even though experiment 2 suggested that their omission was discriminable. Shifting the position of the gate from the onset to the middle portion of the tone impaired overall identification accuracy by 25%. Taken together, these findings confirm the prominent status of onsets in musical instrument identification, but suggest that rapidly varying transients are less indicative of instrument identity compared to the relatively slow buildup of sinusoidal components during onsets.

Modeling the onset advantage in musical instrument recognition.

Sound onsets provide particularly valuable cues for musical instrument identification by human listeners. It has remained unclear whether this onset advantage is due to enhanced perceptual encoding or the richness of acoustical information during onsets. Here this issue was approached by modeling a recent study on instrument identification from tone excerpts [Siedenburg. (2019). J. Acoust. Soc. Am. 145(2), 1078-1087]. A simple Hidden Markov Model classifier with separable Gabor filterbank features simulated human performance and replicated the onset advantage observed previously for human listeners. These results provide evidence that the onset advantage may be driven by the distinct acoustic qualities of onsets.

Timbral Shepard-illusion reveals ambiguity and context sensitivity of brightness perception.

Recent research has described strong effects of prior context on the perception of ambiguous pitch shifts of Shepard tones [Chambers, Akram, Adam, Pelofi, Sahani, Shamma, and Pressnitzer (2017). Nat. Commun. 8, 15027]. Here, similar effects are demonstrated for brightness shift judgments of harmonic complexes with cyclic spectral envelope components and fixed fundamental frequency. It is shown that frequency shifts of the envelopes are perceived as systematic shifts of brightness. Analogous to the work of Chambers et al., the perceptual ambiguity of half-octave shifts resolves with the presentation of prior context tones. These results constitute a context effect for the perceptual processing of spectral envelope shifts and indicate so-far unknown commonalities between pitch and timbre perception.

Modeling Timbre Similarity of Short Music Clips.

There is evidence from a number of recent studies that most listeners are able to extract information related to song identity, emotion, or genre from music excerpts with durations in the range of tenths of seconds. Because of these very short durations, timbre as a multifaceted auditory attribute appears as a plausible candidate for the type of features that listeners make use of when processing short music excerpts. However, the importance of timbre in listening tasks that involve short excerpts has not yet been demonstrated empirically. Hence, the goal of this study was to develop a method that allows to explore to what degree similarity judgments of short music clips can be modeled with low-level acoustic features related to timbre. We utilized the similarity data from two large samples of participants: Sample I was obtained via an online survey, used 16 clips of 400 ms length, and contained responses of 137,339 participants. Sample II was collected in a lab environment, used 16 clips of 800 ms length, and contained responses from 648 participants. Our model used two sets of audio features which included commonly used timbre descriptors and the well-known Mel-frequency cepstral coefficients as well as their temporal derivates. In order to predict pairwise similarities, the resulting distances between clips in terms of their audio features were used as predictor variables with partial least-squares regression. We found that a sparse selection of three to seven features from both descriptor sets-mainly encoding the coarse shape of the spectrum as well as spectrotemporal variability-best predicted similarities across the two sets of sounds. Notably, the inclusion of non-acoustic predictors of musical genre and record release date allowed much better generalization performance and explained up to 50% of shared variance (R2) between observations and model predictions. Overall, the results of this study empirically demonstrate that both acoustic features related to timbre as well as higher level categorical features such as musical genre play a major role in the perception of short music clips.

The role of long-term familiarity and attentional maintenance in short-term memory for timbre.

We study short-term recognition of timbre using familiar recorded tones from acoustic instruments and unfamiliar transformed tones that do not readily evoke sound-source categories. Participants indicated whether the timbre of a probe sound matched with one of three previously presented sounds (item recognition). In Exp. 1, musicians better recognised familiar acoustic compared to unfamiliar synthetic sounds, and this advantage was particularly large in the medial serial position. There was a strong correlation between correct rejection rate and the mean perceptual dissimilarity of the probe to the tones from the sequence. Exp. 2 compared musicians' and non-musicians' performance with concurrent articulatory suppression, visual interference, and with a silent control condition. Both suppression tasks disrupted performance by a similar margin, regardless of musical training of participants or type of sounds. Our results suggest that familiarity with sound source categories and attention play important roles in short-term memory for timbre, which rules out accounts solely based on sensory persistence.

Acoustic and Categorical Dissimilarity of Musical Timbre: Evidence from Asymmetries Between Acoustic and Chimeric Sounds.

This paper investigates the role of acoustic and categorical information in timbre dissimilarity ratings. Using a Gammatone-filterbank-based sound transformation, we created tones that were rated as less familiar than recorded tones from orchestral instruments and that were harder to associate with an unambiguous sound source (Experiment 1). A subset of transformed tones, a set of orchestral recordings, and a mixed set were then rated on pairwise dissimilarity (Experiment 2A). We observed that recorded instrument timbres clustered into subsets that distinguished timbres according to acoustic and categorical properties. For the subset of cross-category comparisons in the mixed set, we observed asymmetries in the distribution of ratings, as well as a stark decay of inter-rater agreement. These effects were replicated in a more robust within-subjects design (Experiment 2B) and cannot be explained by acoustic factors alone. We finally introduced a novel model of timbre dissimilarity based on partial least-squares regression that compared the contributions of both acoustic and categorical timbre descriptors. The best model fit (R (2) = 0.88) was achieved when both types of descriptors were taken into account. These findings are interpreted as evidence for an interplay of acoustic and categorical information in timbre dissimilarity perception.