Does singing have different effects on physiology compared to other vocal activities? In a study conducted together with colleagues of the Department of Behavioural and Cognitive Biology, we examined the association of salivary levels of oxytocin, corticosterone and testosterone with different types of activities conduced solo or in group.

Singing and speaking were associated with decreases in salivary oxytocin concentrations, when performed together or alone, however, oxytocin concentrations decreased by less after singing together than after speaking together. Singing together improved self-perceived emotional status and social connectedness more than speaking together.
You can read the full paper here
Well, I have anecdotal evidence that this is indeed the case. I used to sing in a choir, and it made me very happy to sing. 🙂