Core principles of melodic organisation emerge from transmission chains with random melodies

Music is a product of biological and cultural evolution. One major motor of the latter is cultural transmission, which may play a role in explaining the existence of musical universals. We tested how cultural transmission can shape melodic features in music. Specifically, we investigated whether random melodic seeds, in their transformation, take on properties known to characterise music within or even across cultures. We used iterated learning, a paradigm simulating the transmission of culturally-learned items through a transmission chain with non-musician participants (N=64). We found that melodies vocally reproduced between "generations" became more similar to known musical scales, showed a predominance of consonant intervals, and decreased their number of used scale degrees. Further observed were certain cross-cultural principles relating to interval progressions; as well as, interestingly, features that music shares with speech, such as phrase-final lengthening and Zipfian rank-frequency distributions of signalling units. Converging towards better memorability, participants' vocalisations decreased in entropy, and their contours became smoother and more consistent. Finally, certain short melodic patterns became prominent motifs within incipient musical "traditions", insofar as simulated by the chains. These emerging features may reflect a process shaped by (i) cognitive bottlenecks such as learnability; (ii) statistical properties of the processes and structures involved in inter-generational vocal transmission; but also by (iii) idiosyncratic cultural artefacts specific to the lab samples employed. Overall, our results show that core aspects of melodic organisation, as known from musical cultures around the world, begin to emerge under cultural transmission as simulated in the lab.