Put a group of strangers in a room and ask them to make friends, and it takes weeks. Ask them to sing together, and it takes one session. There is now evidence for that.
Eiluned Pearce, Jacques Launay, and Robin Dunbar followed newly formed adult-education classes over seven months, published in Royal Society Open Science in 2015. Some classes sang together; others did crafts or creative writing. All the groups bonded over time — but the singers felt close to each other much faster. The researchers named it the ice-breaker effect.
The interesting wrinkle is why. In the craft and writing classes, closeness grew through one-on-one conversation, the ordinary slow way people warm up. Singing skipped that. A whole room synchronized on breath and pitch felt bonded before anyone had a real conversation. You do not have to like the person next to you to sing in time with them, and the bonding happens anyway.
Related work from the same group tied group singing to raised pain thresholds, a marker of the endorphin release that underlies social bonding — and found the effect strengthened in larger groups.
The limits are worth stating: these were modest samples of self-selected adults who chose to take a class. Singing is not a magic solvent for every group.
But if you are designing a program meant to knit strangers together fast — a workshop, a residency, a first gathering — the research points at doing something in unison, early. Sing, chant, move together. Conversation can come after the ice is already broken.
Sources
Pearce, E., Launay, J., & Dunbar, R. I. M. (2015). "The ice-breaker effect: singing mediates fast social bonding." Royal Society Open Science. · Weinstein et al. (2016), Evolution and Human Behavior.