Global music recordings support the motor constraint hypothesis for human and avian song contour

There has recently been renewed interest in using quantitative data to explore questions about musical universals. One explanation for certain musical universals is that they reflect ways of singing that are most energetically efficient, as opposed to biological specializations for human music. Previous research found support for this "motor constraint hypothesis" by comparing pitch contour shapes in samples of human and avian songs, but the sample of human songs was limited to notated scores of European and Chinese folk songs from the Essen database. Here we test this hypothesis using a more diverse global sample of human music recordings from the Garland Encyclopedia of World Music. By directly comparing pitch contour shapes in a diverse sample of human songs and bird songs, we found that both human and bird songs tend to employ similar descending/arched melodic contours despite substantial differences in absolute pitch and duration. This preference was consistent for both Western and non-Western songs. Surprisingly, we also found that the global samples of human and bird song contours were significantly more correlated with one another than either was with the Essen contours. Our findings of broad cross-cultural and cross-species parallels support the motor constraint hypothesis for melodic contour. More generally, our findings demonstrate the importance of greater collaboration between ethnomusicology and music psychology.