Music therapy can be used for a wide range of illnesses, cognitive problems, and emotional issues. Because of the positive reactions of music therapy patients, a large amount of music therapy research has been done to test the theories behind why, how and if music therapy actually works. While the results differ with the various applications and techniques, in general music therapy research has established that music therapy is an acceptable and legitimate health care profession.

There has been extensive music therapy research done on various areas of the health care field, and some of the most difficult patients with the most difficult to treat problems have shown improvement, if sometimes temporary, when they have been exposed to music therapy. For example, Alzheimer's patients suffer from numerous problems such as cognitive dysfunctions, social behavior issues, and motor skill problems. In music therapy research, cognitive dysfunction in Alzheimer's patients is treated by subjecting the patient to three different types of music therapy treatments: musically cued reminiscence, verbally cued reminiscence, and musical activity. While musically and verbally cued reminiscence did improve certain brain functions and even could increase language abilities in some patients, the most significant difference was found in patients who were exposed to musical activities. In fact, music therapy research showed that these musical activities – like using songs to promote reminiscence and discussion – actually raised patients' cognitive testing scores.

But cognitive disabilities and illnesses are not the only health problems that can be treated successfully with music therapy. Music therapy is often used for patients who suffer from chronic pain. In the chronic pain studies, different types of pain patients were studied to see how music therapy would improve pain problems caused by various medical problems. Chronic pain patients in general are helped by music therapy because the perception of pain and the perception of music are essentially the same in terms of the way the brain perceives each sensation. Music is used to cancel out the vibrations of pain, often eliminating - or at least decreasing - the brain's perception of the pain.

Music therapy has a very high success rate in pain patients who suffer from Parkinson's disease, cancer, and other ongoing illnesses. But there is also a high rate of success when music is used to treat the pain of temporary pain, like the pain of labor and childbirth. In fact, music therapy research shows that when used in the labor and delivery room, music can help a laboring mother to lower her amount of pain. Cancer patients, especially children, are often exposed to music therapy treatments that involve singing; this treatment has been shown to boost the child's immune system.