"Does singing promote well-being?: An empirical study of professional and amateur singers during a singing lesson."
And there's a bit more on that on CBC's The Current. Scroll down to "Work and Music."
Ironically, the documentary producer who's focusing on music has chosen a highly conventional set of songs... but perhaps her intent is to illustrate the effects of music via familiarity rather than via novelty.
It's a good doc, though.