The evolution of music, speech, and sociality have been debated since before Darwin. The social bonding hypothesis proposes that these phenomena may be interlinked: musicality may have facilitated the evolution of social bonding beyond the possibilities of spoken language. Although dozens of experimental studies have argued that synchronised rhythms can promote bonding, methodological issues including publication bias, sample bias, experimenter effects, and appropriateness of experimental controls make it unclear whether synchronous singing reliably and generally enhances bonding relative to speaking. Here, we propose a Registered Report to overcome these issues through a global experiment in diverse languages aiming to collect data from 1800 participants across 60 sites. The social bonding hypothesis predicts that bonding will increase more after synchronous singing than after spoken (sequential) conversation or (simultaneous) recitation, while alternative hypotheses predict that song will not increase bonding relative to speech. Regardless of outcome, these results will provide an unprecedented understanding of cross-cultural relationships between music, speech, and sociality.