The evolution of music, language, and cooperation have been debated since before Darwin. The social bonding hypothesis proposes that these phenomena may be interlinked: musicality may have facilitated the evolution of group cooperation beyond the possibilities of spoken language. Although dozens of experimental studies have shown that synchronised rhythms can promote cooperation, it is unclear whether synchronous singing enhances cooperation relative to spoken language, particularly across diverse societies that differ in their musical/linguistic rhythms and social organisation. Here, we propose a Registered Report to test this hypothesis through a global experiment in diverse languages aiming to collect data from 1500 participants across 50 sites. The social bonding hypothesis predicts that cooperation will increase more after synchronous singing than after spoken (sequential) conversation or (simultaneous) recitation, while alternative hypotheses predict that song will not increase cooperation relative to speech. Regardless of outcome, these results will provide an unprecedented understanding of cross-cultural relationships between music, language, and cooperation.