I would imagine that music, even background music in a psychiatric hospital could soothe agitation and alleviate sadness in patients – for a while anyhow. It could also help provide a calm environment amongst the pervading chaos felt by a patient in one of these hospitals.
I know of someone who recruited others to join her and later reported that being involved with music gave them all a great deal of pleasure as well as relaxation. They composed songs communally and felt that they had achieved something positive. After their first CD came out, with help of course, they felt so much more confident in their abilities to achieve something. Some of the subjects they chose to sing about included: understanding, removing stigma and living with a mental illness. They stressed that working together was preferable to doing the same thing alone.