Singing Good For YouJoyce sent this link an article in the on-line version of Andante magazine. The article is brief, and of interest. It reports on a study that suggests that singing has health benefits.
Blood samples were taken after a choir sang Mozart's Requiem; and a week later, when the same choir merely listened the a recording of the Requiem. The first samples had increased factors for a well-functioning immune system; the second samples did not.
I'd want to read more of this study, to be published in the Journal of Behavioural Medicine. It immediately occurs to me that, given the week intervening time, other factors may have influenced the blood chemistry.
But, it is a fun idea. My non-scientific personal experience is that singing makes me feel better.