Music therapy is both an allied health profession and a field of scientific research which studies correlations between the process of clinical therapy and biomusicology, musical acoustics, music theory, psychoacoustics and comparative musicology. It is an interpersonal process in which a trained music therapist uses music and all of its facets—physical, emotional, mental, social, aesthetic, and spiritual—to help clients to improve or maintain their health. Music therapists primarily help clients improve their observable level of functioning and self-reported quality of life in various domains (e.g., cognitive functioning, motor skills, emotional and affective development, behavior and social skills) by using music experiences (e.g., singing, songwriting, listening to and discussing music, moving to music) to achieve measurable treatment goals and objectives. Referrals to music therapy services may be made by a treating physician or an interdisciplinary team consisting of clinicians such as physicians, psychologists, physical therapists, and occupational therapists.
Music therapists are found in nearly every area of the helping professions. Some commonly found practices include developmental work (communication, motor skills, etc.) with individuals with special needs, songwriting and listening in reminiscence/orientation work with the elderly, processing and relaxation work, and rhythmic entrainment for physical rehabilitation in stroke victims.
The Turco-Persian psychologist and music theorist al-Farabi (872–950), known as "Alpharabius" in Europe, dealt with music therapy in his treatise Meanings of the Intellect, where he discussed the therapeutic effects of music on the soul. Robert Burton wrote in the 17th century in his classic work, The Anatomy of Melancholy, that music and dance were critical in treating mental illness, especially melancholia.
It is considered one of the expressive therapies.
There are a few different philosophies of thought regarding the foundations of Music Therapy. One is based on education and two are based on music therapy itself, both of which will only be briefly covered here. In addition, there are philosophies based on psychology, and one based on neuroscience.
Different approaches from education are Orff-Schulwerk (Orff), Dalcroze Eurhythmics, and Kodaly. The two philosophies that developed directly out of music therapy are Nordoff-Robbins and the Bonny Method of Guided Imagery and Music. 
Music therapists work many times with individuals who have behavioral-emotional disorders. To meet the needs of this population, music therapists have taken current psychological theories and used them as a basis for different types of music therapy. Different models include behavioral therapy, cognitive behavioral therapy, and psychodynamic therapy.
The therapy model based on neuroscience is called Neurological Music Therapy (NMT). A definition of NMT is "NMT is based on a neuroscience model of music perception and production, and the influence of music on functional changes in nonmusical brain and behavior functions." In other words, NMT studies how the brain is without music, how the brain is with music, measures the differences, and uses these differences to cause changes in the brain through music that will eventually effect the client non-musically. As internationally known professor and researcher Dr. Thaut said, "The brain that engages in music is changed by engaging in music."
Music therapy has existed in its common current form in the United States since around 1944, when the first undergraduate degree program in the world was founded at Michigan State University and the first graduate degree program at the University of Kansas. The American Music Therapy Association (AMTA) was founded in 1998 as a merger between the National Association for Music Therapy (NAMT, founded in 1950) and the American Association for Music Therapy (AAMT, founded in 1971). Numerous other national organizations exist, such as the Institute for Music and Neurologic Function, Nordoff-Robbins Center For Music Therapy and The Bonny Foundation. In the United States, a music therapist is most commonly designated by MT-BC (Music Therapist-Board Certified). A music therapist may use ideas or concepts from different disciplines such as speech/language, physical therapy, medicine, nursing, education, and so forth.
A music therapist may have different credentials or professional licenses and may also have a master's degree in music therapy or in another clinical field (social work, mental health counseling, or the like). New York State requires that people holding the title music therapist be licensed as a creative arts therapist by holding a master's degree or higher in the field. Other masters degree holders may also take a test administered by the state of New York. Some practicing music therapists have held Ph.D.s in non-music-therapy (but related) areas, but more recently Temple University and Lesley University have founded a true music therapy Ph.D. program. A music therapist will typically practice in a manner that incorporates music therapy techniques with broader clinical practices such as assessment, diagnosis, psychotherapy, rehabilitation, and other practices depending on population. Music therapy services rendered within the context of a social service, educational, or health care agency are reimbursable by insurance and sources of funding for individuals with certain needs, under the title of Activity Therapy. Music therapy services have been identified as reimbursable under Medicaid, Medicare, Private insurance plans and other services such as state departments and government programs.
A US music therapist may also hold the designation of CMT, ACMT, or RMT—initials which were previously conferred by the now-defunct AAMT and NAMT. More current music therapists hold the designation, MT-BC, music therapist-board certified, given by the Certification Board of Music Therapists. A degree in music therapy requires proficiency in guitar, piano, voice, music theory, music history, reading music, improvisation, as well as varying levels of skill in assessment, documentation, and other counseling and health care skills depending on the focus of the particular university's program.
To become board-certified in the United States, a music therapist must complete course work at an accredited ATMA program at a college or university, successfully complete a 1040 hour Music Therapy internship, and pass the Certifying Board examination. Board Certified Music Therapists are required to maintain their education through continuing education courses, called Continuing Music Therapy Education courses, or CMTEs. These classes fall under the purview of the Certification Board for Music Therapists to assure quality and applicability. They are offered at the state, regional, and national level.
Live music was used in hospitals after both of the World Wars, as part of the regime for some recovering soldiers. Clinical Music therapy in Britain as it is understood today was pioneered in the 60s and 70s by French cellist Juliette Alvin, whose influence on the current generation of British music therapy lecturers remains strong. Mary Priestley, one of Juliette Alvin's students came to discover/create Analytical Music Therapy. Analytical Music Therapy is a form of Music Therapy which together with the Nordoff-Robbins school of Music Therapy, form the two central forms of Music Therapy used today. Mary Priestley's books: Music Therapy in Action, first published by Constable and company 1975 (ISBN 0 09 459900 9) and Essays on Analytical Music Therapy, Barcelona Publishers ©1994.(ISBN 0-9624080-2-6) Form part of the core course work for students of Analytical Music Therapy all over the world.
The Nordoff-Robbins approach to music therapy developed from the work of Paul Nordoff and Clive Robbins in the 1950/60s. It is grounded in the belief that everyone can respond to music, no matter how ill or disabled. The unique qualities of music as therapy can enhance communication, support change, and enable people to live more resourcefully and creatively. Nordoff-Robbins now run music therapy sessions throughout the UK, US, South Africa, Australia and Germany. Its head quarters are in London where it also provides training and further education programmes, including the only PhD course in music therapy available in the UK. Music therapists, many of whom work with an improvisatory model (see clinical improvisation), are active particularly in the fields of child and adult learning disability, but also in psychiatry and forensic psychiatry, geriatrics, palliative care and other areas.
Practitioners are registered with the Health Professions Council  and from 2007 new regisrants must normally hold a masters degree in music therapy. There are masters level programmes in music therapy in Bristol, Cambridge, Cardiff, Edinburgh and London, and there are therapists throughout the United Kingdom. The professional body in the UK is the Association of Professional Music Therapists  while the British Society for Music Therapy  is a charity providing information about music therapy.
In 2002, the World Congress of Music Therapy was held in Oxford, on the theme of Dialogue and Debate.  In November 2006, Dr. Michael J. Crawford  and his colleagues again found that music therapy helped the outcomes of Schizophrenic patients.  In 2009, he and his team were researching the usefulness of improvisational music in helping patients with agitation and also those with Dementia.
Music has been shown to affect portions of the brain. Part of this therapy is the ability of music to affect emotions and social interactions. Research by Nayak et al. showed that music therapy is associated with a decrease in depression, improved mood, and a reduction in state anxiety. Both descriptive and experimental studies have documented effects of music on quality of life, involvement with the environment, expression of feelings, awareness and responsiveness, positive associations, and socialization . Additionally, Nayak et al. found that music therapy had a positive effect on social and behavioral outcomes and showed some encouraging trends with respect to mood.
More recent research suggests that music can increase patient’s motivation and positive emotions.  Current research also suggests that when music therapy is used in conjunction with traditional therapy it improves success rates significantly. Therefore, it is hypothesized that music therapy helps stroke victims recover faster and with more success by increasing the patient’s positive emotions and motivation, allowing them to be more successful and driven to participate in traditional therapies.
Research has shown the ability of music therapy to increase positive social interactions, positive emotions, and motivation in stroke patients. Wheeler et al. found that group music therapy sessions increased the ease at which stroke patients responded to social interaction and increased positive attitude reports from patient families, while individual sessions helped to motivate patients for treatment. Another study examined the effect of music therapy on mood of stroke patients and found similar results that showed decreased anxiety, fatigue, and hostile mood states . Additionally, Nayak et al. found improved social interaction (more actively involved and cooperative) when music therapy was used in stroke recovery programs.
Recent studies have examined the effect of music therapy on stroke patients, when combined with traditional therapy. One study found the incorporation of music with therapeutic upper extremity exercises gave patients more positive emotional effects than exercise alone. In another study, Nayak et al. found that rehabilitation staff rated participants in the music therapy group were more actively involved and cooperative in therapy than those in the control group. Their findings gave preliminary support to the efficacy of music therapy as a complementary therapy for social functioning and participation in rehabilitation with a trend toward improvement in mood during acute rehabilitation.
Although positive changes have been associated with music therapy, some considerations must be taken into account. While scientists have determined that a variety of physiological and psychological changes occur when listening to music, broad conclusions cannot yet be made concerning the relationship and the direction of the relationship between music and emotion. Additionally, there may be mediating factors which affect the success of music therapy. For example, Nayak et al. found the more impaired an individual’s social behavior was at the outset of treatment, the more likely he or she was to benefit from music therapy. Additionally, they noted the effectiveness of music therapy may be moderated by the time frame of the treatment. It is possible that music therapy has a more pronounced effect on mood the closer to injury it is applied.
Current research shows that when music therapy is used in conjunction with traditional therapy, it improves rates of recovery, and emotional and social deficits resulting from stroke.  A study by Jeong & Kim examined the impact of music therapy when combined with traditional stroke therapy in a community-based rehabilitation program.  Thirty-three stroke survivors were randomized into one of two groups: the experimental group, which combined rhythmic music and specialized rehabilitation movement for eight weeks; and a control group, that received referral information for traditional therapy (and were assumed to have sought traditional therapy). The results of this study showed that participants in the experimental group gained more flexibility, wider range of motion, more positive moods, and increased frequency and quality of social interactions.
Music has also been used in recovery of motor skills. Rhythmical auditory stimulation in a musical context in combination with traditional gait therapy improved the ability of stroke patients to walk. The study consisted of two treatment conditions, one which received traditional gait therapy and another which received the gait therapy in combination with the rhythmical auditory stimulation. During the rhythmical auditory stimulation, stimulation was played back measure by measure, and was initiated by the patient’s heel-strikes. Each condition received fifteen sessions of therapy. The results revealed that the rhythmical auditory stimulation group showed more improvement in stride length, symmetry deviation, walking speed and rollover path length (all indicators for improved walking gait) than the group that received traditional therapy alone.
Schneider et al. also studied the effects of combining music therapy with standard motor rehabilitation methods. In this experiment, researchers recruited stroke patients without prior musical experience and trained half of them in an intensive step by step training program that occurred fifteen times over three weeks, in addition to traditional treatment. These participants were trained to use fine both fine and gross motor movements by learning how to use the piano and drums. The other half of the patients received only traditional treatment over the course of the three weeks. Three-dimensional movement analysis and clinical motor tests showed participants who received the additional music therapy had significantly better speed, precision, and smoothness of movements as compared to the control subjects. Participants who received music therapy also showed a significant improvement in every-day motor activities as compared to the control group . Wilson, Parsons, & Reutens looked at the effect of melodic intonation therapy (MIT) on speech production in a male singer with severe Broca’s aphasia. In this study, thirty novel phrases were taught in three conditions: unrehearsed, rehearsed verbal production (repetition), or rehearsed verbal production with melody (MIT). Results showed that phrases taught in the MIT condition had superior production, and that compared to rehearsal, effects of MIT lasted longer.
Another study examined the incorporation of music with therapeutic upper extremity exercises on pain perception in stroke victims . Over the course of eight weeks, stroke victims participated in upper extremity exercises (of the hand, wrist, and shoulder joints) in conjunction with one of the three conditions: song, karaoke accompaniment, and no music. Patients participated in each condition once, according to a randomized order, and rated their perceived pain immediately after the session. Results showed that although there was no significant difference in pain rating across the conditions, video observations revealed more positive affect and verbal responses while performing upper extremity exercises with both music and karaoke accompaniment . Nayak et al.  examined the combination of music therapy with traditional stroke rehabilitation and also found the addition of music therapy improved mood and social interaction. Participants who had suffered traumatic brain injury or stroke were placed in one of two conditions: standard rehabilitation or standard rehabilitation along with music therapy. Participants received three treatments per week for up to ten treatments. Therapists found that participants who received music therapy in conjunction with traditional methods had improved social interaction and mood.
Some music may reduce heart rate, respiratory rate, and blood pressure in patients with coronary heart disease, according to a 2009 Cochrane review of 23 clinical trials . Benefits included a decrease in blood pressure, heart rate, and levels of anxiety in heart patients. However, the effect was not consistent across studies, according to Joke Bradt, Ph.D., and Cheryl Dileo, Ph.D., both of Temple University in Philadelphia. Music did not appear to have much effect on patients' psychological distress. "The quality of the evidence is not strong and the clinical significance unclear," the reviewers cautioned. In 11 studies patients were having cardiac surgery and procedures, in nine they were MI patients, and in three cardiac rehabilitation patients. The 1,461 participants were largely white (average 85%) and male (67%). In most studies, patients listened to one 30-minute music session. Only two used a trained music therapist instead of prerecorded music.
Music therapist, music researcher and experimental composer Enrico Curreri clinically explored theories and concepts developed by the American composer John Cage. For example, in various music therapy sessions with a patient diagnosed with depression and anxiety disorder, Curreri performed Cage’s seminal composition of silence 4 33 and utilized aleatoric/chance procedures. In addition, Curreri has been clinically investigating experimental music/sound/noise music, free improvisation and microtonal music to help assist in understanding the process of creativity.
But to leave all declamatory speeches in praise  of divine music, I will confine myself to my proper subject: besides that excellent power it hath to expel many other diseases, it is a sovereign remedy against  despair and melancholy, and will drive away the devil himself. Canus, a Rhodian fiddler, in  Philostratus, when Apollonius was inquisitive to know what he could do with his pipe, told him, "That he would make a melancholy man merry, and him that was merry much merrier than before, a lover more enamoured, a religious man more devout." Ismenias the Theban,  Chiron the centaur, is said to have cured this and many other diseases by music alone: as now they do those, saith  Bodine, that are troubled with St. Vitus's Bedlam dance.