Music therapists work in many different settings with a variety of populations. A bachelor's degree in music therapy or an equivalency certificate (in addition to a bachelor's degree in another field of study) from an accredited university, along with the completion of 1,040 internship hours, are required to practice music therapy. This training imparts a knowledge of music history and theory; the psychology, anatomy, and physiology of musical responses; and various diseases and disabilities. Following formal education and internship, therapists must pass a nationally standardized certification exam in order to obtain the credential MT-BC, identifying them as board certified music therapists. Some therapists carry state licenses as well, depending on the state in which they work. Continuing education requirements also ensure that a therapist's skill level always reflects the quality standard set forth by the certification board for music therapists.