Music therapy is an interpersonal process in which a trained therapist uses music and all of its facets—physical, emotional, mental, social, aesthetic, and spiritual—to help clients to improve or maintain their health. In some instances, the client's needs are addressed directly through music; in others they are addressed through the relationships that develop between the client and therapist. Music therapy is used with individuals of all ages and with a variety of conditions, including: psychiatric disorders, medical problems, physical disabilities, sensory impairments, developmental disabilities, substance abuse issues, communication disorders, interpersonal problems, and aging. It is also used to improve learning, build self-esteem, reduce stress, support physical exercise, and facilitate a host of other health-related activities. Music therapists may encourage clients to sing, play instruments, create songs, or do other musical activities.