The Journal of the Southern Medical Association - Southern Medical Journal - published a continuing medical education topic "Music as Therapy" in its March 2005 issue discussing many aspects of the effect of music on the ill, the anxious recipients of medical procedures, newborns and caregivers, with an extensive bibliography and literature list. The journal should be available in local hospital libraries or reprints may be obtained from the lead author.
Her address is on the article or I can send it to whoever would like it. I would certainly agree that informal Music as Therapy is different from formal Music Therapy and can be provided by volunteers, caregivers, both professional and those thrust into the role by circumstances and by anyone who can hum a favorite tune or a lullaby at the bedside.