The term popular music is extremely vague, covers a wide field of musical endeavour and ranges over a long period of time; there has been “popular music” ever since man made music for his own pleasure. The difficulty is to draw a distinction between serious or, less accurately, classical music and the other forms in existence, especially as much of the material in the popular field is taken quite seriously by many people.

Progressive rock & progressive metal. These are two major divisions of prog music from which many other categories can be sub-classified. Basically, prog metal will combine elements of heavy metal (such as heavily distorted guitars and fast rhythms) with some or all of those prog traits outlined in the above section, while prog rock combines a less "edgy" (rock / hard rock) sound with those aforementioned characteristics.

Music Therapy is the clinical and evidence-based use of music interventions to accomplish individualized goals within a therapeutic relationship by a credentialed professional who has completed an approved music therapy program. Music Therapy is an established health profession in which music is used within a therapeutic relationship to address physical, emotional, cognitive, and social needs of individuals.