Transition of complexity in vocal melody based on Japanese hit charts over half a century

Abstract

Recent technical advances provide an opportunity to study the cultural evolution of music using quantitative methods. Previous computational social science research of popular music mainly examined the history of the Billboard hit chart. However, Japanese popular music remains underexplored despite its large market and distinct cultural context. The present study examined pitch and rhythm feature trajectories using Music instrument digital interface (MIDI) melodic transcriptions of Japanese hit songs (1977–2024), employing methods consistent with prior Billboard analyses (Hamilton & Pearce, 2024). The result identified significant quantitative turning points, or “melodic revolutions,” around 2008, distinct from the revolution in Billboard hits. The revolution aligns with the rise of idol-group popularity, which may reflect specific production and consumption patterns. Further derivative analysis revealed that recent Japanese hits showed rapidly increasing pitch melodic unpredictability, possibly coinciding with the growing influence of Vocaloid culture on mainstream Japanese popular music. Cross-cultural comparisons with vocal melody in the Billboard chart revealed that pitch features evolved uniquely within Japanese popular music, while rhythm features exhibited similar trends in both cultures. Moreover, Japanese hit charts showed higher information content values representing unpredictability than Billboard hit charts from 1996. These findings shed light on Japan’s distinctive musical evolution, and rising preferences for complex and unpredictable melodies may enhance the uniqueness and creativity of Japanese popular music.