I found on the Internet a statement by the Harvard psychologist Steven Pinker that astounded me: music "as far as biological cause and effect are concerned is useless." I don't know the context of his argument, but I suspect many experts will sharply disagree.
Everything in my experience and reading shows that, as Shakespeare said, "music hath charms to soothe the savage breast" (or beast; we' not sure).
Just yesterday, feeling wound up, I listened to K.D. Lang and Tony Bennett in a wonderful duet of the old pop song, "Because of You." It is done with the slowness of a classical adagio (think Barber, Mahler, Beethoven...) or the piano nocturnes of Chopin or Satie. The effect was, of course, calming.
I have no doubt that a loud march or bit of heavy metal would have the opposite effect if I wanted to increase my productivity.
I did a quick check on Google to see if I was going crazy or if Pinker could be right. An article in the Journal of Cardiovascular Nursing concludes that music therapy reduces pain and anxiety in patients recovering from heart surgery. A non-scholarly article listed a whole list of physiological benefits of music, from decreasing blood pressure, improving sleep, reducing headaches, helping memory and brain functions, boosting immunity, etc.
The psychological effects of music, like those of meditation and prayer, have been shown to increase inner peace, reduce stress, anxiety and depression, among others. What type of music is involved in such studies?
Not only Mozart but many other forms of music, including chant. It seems to me the slower and softer the better because relaxation as well as meditation involves reducing the fast pace of daily life. The Slow Movement that began with food in Italy now includes many other aspect of practical wisdom, based on the fact that the fundamental human restlessness and the speed of our lives causes stress that harms body and mind.
As I write this, I have a quiet string quartet by Mozart playing. A day without music would be a day without light or air; all are essential for life in our anxious age. I cannot argue on a scientific basis with Pinker's quoted statement, but I know that my experience with music "soothing the savage breast" is universal.