@techreport{oai:ipsj.ixsq.nii.ac.jp:02009796,
 author = {Kaikwan,Lau and Kaikwan Lau},
 issue = {23},
 month = {May},
 note = {This study investigates whether the Vocaloid music community, centered around the virtual singer Hatsune Miku, has favored progressively faster and more compact songs in its most popular output over the period 2007-2025. We analyzed 1,900 songs (100 per year, ranked by community score) using librosa-based audio feature extraction, yielding 12 acoustic metrics spanning tempo, rhythm, energy, spectral, and harmonic dimensions. Mann-Kendall trend tests on yearly aggregates revealed statistically significant trends in 8 of 12 metrics: BPM increased modestly (+2.3%, p = 0.004), while onset density (+6.4%, p = 0.010), rhythm complexity (+9.1%, p < 0.001), and harmonic change rate (+8.0%, p = 0.042) rose more substantially. Song duration decreased by 6.8% (p = 0.002), with the sharpest decline after 2020. Tempo stability showed a small but highly significant decrease (p < 0.001). These findings suggest that the perceived acceleration of Vocaloid music is driven less by raw tempo increases and more by structural compression: shorter songs, denser note content, and more complex rhythmic patterns. We discuss these trends in the context of short-form video platforms and evolving listener attention patterns., This study investigates whether the Vocaloid music community, centered around the virtual singer Hatsune Miku, has favored progressively faster and more compact songs in its most popular output over the period 2007-2025. We analyzed 1,900 songs (100 per year, ranked by community score) using librosa-based audio feature extraction, yielding 12 acoustic metrics spanning tempo, rhythm, energy, spectral, and harmonic dimensions. Mann-Kendall trend tests on yearly aggregates revealed statistically significant trends in 8 of 12 metrics: BPM increased modestly (+2.3%, p = 0.004), while onset density (+6.4%, p = 0.010), rhythm complexity (+9.1%, p < 0.001), and harmonic change rate (+8.0%, p = 0.042) rose more substantially. Song duration decreased by 6.8% (p = 0.002), with the sharpest decline after 2020. Tempo stability showed a small but highly significant decrease (p < 0.001). These findings suggest that the perceived acceleration of Vocaloid music is driven less by raw tempo increases and more by structural compression: shorter songs, denser note content, and more complex rhythmic patterns. We discuss these trends in the context of short-form video platforms and evolving listener attention patterns.},
 title = {Are Vocaloid Songs Getting Denser? A Longitudinal Audio Analysis of 1,900 Hatsune Miku Songs (2007-2025)},
 year = {2026}
}