The critical role of melody and harmony in sleep induction: Direct evidence from electroencephalogram-based analysis

Insomnia, prevalent in contemporary society, is characterized by difficulties in sleep initiation and maintenance, leading to fatigue, depression, and impaired cognitive function. Although research has demonstrated the sleep induction effects of certain musical genres, the neurophysiological mechanisms through which musical constituents, namely, melody, harmony, and rhythm, induce sleep remain inconclusive. To elucidate how musical constituents influence sleep onset, we used both subjective and objective measures, including the Pittsburgh Sleep Quality Index and Karolinska Sleepiness Scale as the former and electroencephalography (EEG) analysis as the latter. The EEG data showed that melody and harmony significantly enhance sleep quality, particularly impacting the theta band and the dispersion entropy in the temporal lobes. Conversely, the effect of rhythm in sleep induction appeared less significant, with minimal activity observed in the frontal and parietal lobes. We believe the data provide a foundation for innovative approaches to music composition that emphasize melody and harmony to enhance the therapeutic potential of music in sleep management, while de-emphasizing the role of rhythm. The findings also support adapting traditional musical forms, such as classical music, for sleep induction purposes and the development of sleep aid music composition rooted in Western music theory.