The role of population size in folk tune complexity

A positive correlation between population size and cultural complexity is perhaps one of the most consistent findings in the field of cultural evolution. However, previous findings are largely based on studies of technology and are not necessarily generalisable across diverse cultural domains. We investigate the relationship between population size and complexity in music using Irish folk session tunes as a case study. Using analyses of a large online folk tune dataset, we show that tunes played by larger communities of musicians have diversified into a greater number of different versions but are intermediate in melodic complexity. These results suggest that while larger populations create more frequent opportunities for musical innovation, they encourage convergence upon intermediate levels of melodic complexity due to a widespread inverse U-shaped relationship between complexity and aesthetic preference. Our results show that the relationship between population size and cultural complexity is domain-dependent, rather than universal.