Persons respond to music if it is important to them, and it is music that is appropriate. I think we have to be certain that music can influence physical, psychological and social responses. It is important to know that music does not heal, but the application of music can remediate certain responses or reactions. This is the music to which they are most likely to make the strongest response. Therefore, music therapists are musicians who are very knowledgeable about a wide range of music types and are capable of producing music live as well as in recordings.
Music is therapeutic because it has the power to influence physical and emotional responses.
Each time a physical change is made, e.g. changes in heart rate, respiration, there is an emotional feeling associated with it. Also, when an emotion is shifted, there is a physical response as well. When this influence is coupled with knowledgeable application, there are desirable outcomes that remediate and or ameliorate and are, therefore, therapeutic. There is a range of persons who can benefit from both of these applications. Generally, music therapists have worked with persons who have illness, physical and otherwise.