Empirical investigations of subjective and cardiac responses to music date back over 125 years. However, the literature has been plagued by methodological/interpretive pitfalls. Most investigations have not “recomposed” music along a particular dimension (e.g., tempo), but rather used unique pieces of music that vary along a number of dimensions (genre, instrumentation, dynamics), adding potential confounds. Additionally, the utility of measuring mean heart rate (HR) changes to music is not particularly strong: for as many studies that report significant effects of music on HR, nearly an equal number report a null effect.
The present study used two less-frequently investigated indices of cardiac activity—HR variability (HRV) and phasic HR—which are known to index parasympathetic nervous system activity. Higher baseline levels of HRV have been consistently linked with greater health and emotional well-being, and increased cognitive flexibility. Phasic HR refers to beat-by-beat changes in HR, and indexes adjustments in attention and emotional processing. Three experiments used the same general class of stimuli: MIDI performances of piano ragtime, recomposed at 60, 90, and 120 beats per minute.
To examine the role of individual differences in HRV and its relationship to responses to music, median split and trend value analyses were performed. Trend value analysis applies the logic and formulas of group trend analysis to individual subjects.
Experiment 1 utilized 2.5-min excerpts of music, and found that HRV decreased as tempo increased, indicating greater parasympathetic withdrawal to faster music. Importantly, no significant relationship was found between tempo and mean HR. Furthermore, as revealed by median split and trend value analyses, tempo had a larger and more consistent effect on HRV in subjects with higher baseline HRV.
Experiment 2 utilized 12–16-s excerpts of music, and found that phasic IBI waveforms increased with tempo. Waveforms were larger for subjects with high baseline HRV than low baseline HRV. Further analysis of the variability of IBI data revealed that variability significantly increased with tempo only for subjects with high baseline HRV.
Experiment 3 utilized 6–8-s of music, and found that reaction times (RTs) to the offset of music decreased as tempo increased. Median split and trend value analyses revealed that the effect of tempo on RT was larger for subjects with high baseline HRV.
Together, these results point to the importance of tempo on physiological response, and the role of individual differences in response to music.