Effects of microtiming deviations between two instruments on the groove experience

Abstract

There is a pleasant component in music often called the ‘groove’ that compels the body to move. Previous studies have discussed syncopation and microtiming deviations (MTD) as musical factors that can affect the groove experience, with research showing the experience to be the greatest when there is no MTD. However, previous works only focused on the magnitude of the MTDs and did not consider MTD resulting from the interaction of two instruments. In addition, the effect of harmony or chord progression on the groove experience remains unclear, despite most groove-based music including harmony. Moreover, little is known about the neural mechanism of groove experience. The present study investigated how the effect of drum MTDs on the groove experience changes with variously added piano patterns. Particularly, we examined the effect of MTD between two instruments and piano harmony. An additional experiment was conducted to measure the EEG response while groove experience. In the pilot experiment, to investigate the effect of drum MTD on the groove experience, five levels of MTD (- 83.3 ms, - 41.6 ms, 0 ms, + 41.6 ms, + 83.3ms) were given to the second and fourth beats in the drum, then the groove experience of the drum stimuli was evaluated. Consistent with previous research, the less the MTD, the higher the groove experience, and the significant difference of the groove was found when the magnitude of MTD was 83.3 ms. In experiment 1, three levels of MTD (- 83.3 ms, 0 ms, + 83.3ms) were applied to drum and piano. In order to make a difference in MTD patterns between instruments, MTDs were given to every note in the piano, whereas MTDs were given only to second and fourth beats in the drum. In the case of the piano, two different chord progressions (single-chord repetition, four-chord repetition) were used, and the groove experience of 18 stimuli was evaluated. Results showed that the effect of piano MTD on the groove experience changes depending on the drum MTD. Especially, the effect of piano MTDs was more significant when the drum MTD was – 83.3 ms. Furthermore, the wanting to move was highly rated when chord progression exists rather than when a single chord is repeated. This suggests that when two instruments are played, the groove experience is influenced not only by the magnitude of the MTDs, but also by the interaction between MTD of each instrument. It was also found that the repeating pattern of chords enhances the groove experience. In experiment 2, to investigate the neural mechanism of groove experience, the spectral power of EEG responses to three stimuli with different degrees of groove (high, medium, and low) were analyzed. We found that the lower the groove, the lower the alpha band power. Given that the reduced alpha power indicates enhanced brain activity, this result suggests that the low level of groove with high MTD increases brain activity by raising the difficulty of processing.