Characteristics of music to improve the quality of sleep

Background: Several studies on the effects of music on sleep disorders have demonstrated that music listening can improve sleep quality in patients with sleep disorders. To our knowledge, nevertheless, none of them have elucidated the characteristics of such music itself.Objective: The purpose of the present study was to elucidate the characteristics of the types of music that improve sleep quality.Methods: In twenty five tracks used in the previous study, we calculated four analysis indicators: scaling exponent of the spectrum of melody's zero-crossings, redundancy of note values, density of notes and tempo.Results: The characteristics of music to improve sleep quality were slow tempo, small change of rhythm, and moderate pitch variation of melody. Based on the results derived from cluster analysis, the music pieces studied were largely categorized into 3 groups. A comparison of these 3 groups showed no significant differences with respect to the scaling exponent of the melody and the density of notes, whereas it showed significant differences with respect to the redundancy of note values and tempo.Conclusions: Our study revealed several characteristics of the types of music that improve sleep quality. The identification of these characteristics contributes to providing personalized music therapy to patients.