When Choirs Sing, Many Hearts Beat As One
“it took almost no time at all for the singers’ heart rates to become synchronized. The readout from the pulse monitors starts as a jumble of jagged lines, but quickly becomes a series of uniform peaks. The heart rates fall into a shared rhythm guided by the song’s tempo“

This has been around a while now, but is still interesting. I wonder if anyone has measured heart rates of supporters at a football or tennis match.
Do guitar ensemble players live longer than soloists? (Only if they follow the conductor!)