The pleasurable desire to move to music, also known as groove, is modulated by rhythmic complexity. How the sensation of groove is influenced by other musical features, such as the harmonic complexity of individual chords, is less clear. To address this, we asked people with a range of musical experience to rate stimuli that varied in both rhythmic and harmonic complexity. Rhythm showed an inverted U-shaped relationship with ratings of pleasure and wanting to move, whereas medium and low complexity chords were rated similarly. Pleasure mediated the effect of harmony on wanting to move and high complexity chords attenuated the effect of rhythm on pleasure. We suggest that while rhythmic complexity is the primary driver, harmony, by altering emotional valence, modulates the attentional and temporal prediction processes that underlie rhythm perception. Investigation of the effects of musical training with both regression and group comparison showed that training increased the inverted U effect for harmony and rhythm, respectively. Taken together, this work provides important new information about how the prediction and entrainment processes involved in rhythm perception interact with musical pleasure.

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Studies comparing musicians and non-musicians have shown that musical training can improve rhythmic perception and production. These findings tell us that training can result in rhythm processing advantages, but they do not tell us whether practicing a particular instrument could lead to specific effects on rhythm perception or production. The current study used a battery of four rhythm perception and production tasks that were designed to test both higher- and lower-level aspects of rhythm processing. Four groups of musicians (drummers, singers, pianists, string players) and a control group of non-musicians were tested. Within-task differences in performance showed that factors such as meter, metrical complexity, tempo, and beat phase significantly affected the ability to perceive and synchronize taps to a rhythm or beat. Musicians showed better performance on all rhythm tasks compared to non-musicians. Interestingly, our results revealed no significant differences between musician groups for the vast majority of task measures. This was despite the fact that all musicians were selected to have the majority of their training on the target instrument, had on average more than 10 years of experience on their instrument, and were currently practicing. These results suggest that general musical experience is more important than specialized musical experience with regards to perception and production of rhythms.

48Groove is defined as the pleasurable desire to move to music. Research has shown that 49 rhythmic complexity modulates the sensation of groove but how other musical features, such as 50 harmony, influence groove is less clear. To address this, we asked people with a range of musical 51 experience to rate stimuli that varied in both rhythmic and harmonic complexity. Rhythm 52 showed an inverted U-shaped relationship with ratings of pleasure and wanting to move, whereas 53 medium and low complexity chords were rated similarly. Pleasure mediated the effect of 54 harmony on wanting to move and high complexity chords attenuated the effect of rhythm. While 55 rhythmic complexity is the primary driver, harmony both modulates the effect of rhythm and 56 makes a unique contribution via its effect on pleasure. These results may be accounted for by 57 predictive processes based on rhythmic and harmonic expectancies that are known to contribute 58 to musical pleasure or reward.When listening to music we often find ourselves tapping or moving along to the beat. 93 This has led to the study of groove, which is the pleasurable desire to move to music [1][2][3]. 94 Certain types of music are more likely to induce the sensation of groove than others. However, 95 which specific aspects of music contribute to this sensation is less clear. Research on groove has 96 focused on rhythmic complexity, and syncopation in particular, showing an inverted U-shaped 97 relationship between degree of syncopation and ratings of pleasure and wanting to move [3]. 98 That is, medium levels of syncopation are rated higher than low or high levels. This research has 99 largely examined rhythm in isolation, but other musical properties likely contribute to the 100 sensation of groove. Harmony in particular may be a strong contributor because it modulates 101 affective responses [4]. However, the extent to which harmony affects groove has not been 102 investigated. Furthermore, few studies have examined the impact of musical training on the 103 sensation of groove. Therefore, in the current study we developed a set of rhythmic stimuli that 104 varied in both their degree of rhythmic and harmonic complexity. We asked people with a broad 105 range of musical training to listen to and rate how much the stimuli made them want to move and 106 how much pleasure they experienced. Our goals were to investigate whether harmonic 107 complexity and its interaction with rhythm affects the sensation of groove. In addition, we 108 investigated the effects of rhythmic complexity and musical training on groove. 109

Groove—defined as the pleasurable urge to move to a rhythm—depends on a fine-tuned interplay between predictability arising from repetitive rhythmic patterns, and surprise arising from rhythmic deviations, for example in the form of syncopation. The perfect balance between predictability and surprise is commonly found in rhythmic patterns with a moderate level of rhythmic complexity and represents the sweet spot of the groove experience. In contrast, rhythms with low or high complexity are usually associated with a weaker experience of groove because they are too boring to be engaging or too complex to be interpreted, respectively. Consequently, the relationship between rhythmic complexity and groove experience can be described by an inverted U-shaped function. We interpret this inverted U shape in light of the theory of predictive processing and provide perspectives on how rhythmic complexity and groove can help us to understand the underlying neural mechanisms linking temporal predictions, movement, and reward. A better understanding of these mechanisms can guide future approaches to improve treatments for patients with motor impairments, such as Parkinson’s disease, and to investigate prosocial aspects of interpersonal interactions that feature music, such as dancing. Finally, we present some open questions and ideas for future research.

The sensation of groove can be defined as the pleasurable urge to move to rhythmic music. When moving to the beat of a rhythm, both how well movements are synchronized to the beat, and the perceived difficulty in doing so, are associated with groove. Interestingly, when tapping to a rhythm, participants tend to overestimate their synchrony, suggesting a potential discrepancy between perceived and measured synchrony, which may impact their relative relation with groove. However, these relations, and the influence of syncopation and musicianship on these relations, have yet to be tested. Therefore, we asked participants to listen to 50 drum patterns with varying rhythmic complexity and rate their sensation of groove. They then tapped to the beat of the same drum patterns and rated how well they thought their taps synchronized with the beat. Perceived synchrony showed a stronger relation with groove ratings than measured synchrony and syncopation, and this effect was strongest for medium complexity rhythms. We interpret these results in the context of meter-based temporal predictions. We propose that the certainty of these predictions determine the weight and number of movements that are perceived as synchronous and thus reflect rewarding prediction confirmations.

The inverted U hypothesis in music predicts that listeners prefer intermediate levels of complexity. However, the shape of the liking response to harmonic complexity and the effect of musicianship remains unclear. Here, we tested whether the relationship between liking and harmonic complexity in single chords shows an inverted U shape and whether this U shape is different for musicians and non-musicians. We recorded these groups’ liking ratings for four levels of harmonic complexity, indexed by their level of acoustic roughness, as well as several measures of inter-individual difference. Results showed that there is an inverted U-shaped relationship between harmonic complexity and liking in both musicians and non-musicians, but that the shape of the U is different for the two groups. Non-musicians’ U is more left-skewed, with peak liking for low harmonic complexity, while musicians’ U is more right-skewed, with highest ratings for medium and low complexity. Furthermore, musicians who showed greater liking for medium compared to low complexity chords reported higher levels of active musical engagement and higher levels of openness to experience. This suggests that a combination of practical musical experience and personality is reflected in musicians’ inverted U-shaped preference response to harmonic complexity in chords.

The pleasurable urge to move to music (PLUMM) elicits activity in motor and reward areas of the brain and is thought to be driven by predictive processes. Dopamine within motor and limbic cortico-striatal networks is implicated in the predictive processes underlying beat-based timing and music-induced pleasure, respectively. This suggests a central role of cortico-striatal dopamine in in PLUMM. This study tested this hypothesis by comparing PLUMM in Parkinson's disease patients, healthy age-matched, and young controls. Participants listened to musical sequences with varying rhythmic and harmonic complexity (low, medium, high), and rated their experienced pleasure and urge to move to the rhythm. In line with previous results, healthy younger participants showed an inverted U-shaped relation between rhythmic complexity and ratings, with a preference for medium complexity rhythms, while age-matched controls showed a similar, but weaker, inverted U-shaped response. Conversely, PD patients showed a significantly flattened response for both the urge to move and pleasure. Crucially, this flattened response could not be attributed to differences in rhythm discrimination and did not reflect an overall decrease in ratings. Together, these results support the role of dopamine within cortico-striatal networks in the predictive processes that form the link between the perceptual processing of rhythmic patterns, and the affective and motor responses to rhythmic music.