The American Guild of Musical Artists (AGMA) was founded March 11, 1936 by a prominent group of solo musical artists including Lawrence Tibbett, Alma Gluck and Jascha Heifetz. Tibbett was to serve as AGMA's president and Heifetz and Gluck as vice-presidents. Among the founding members were Kirsten Flagstad, John McCormack, Andres Segovia, George Gershwin, Fred Waring and Paul Whiteman. The advisory board included Walter Damrosch, Lauritz Melchoir, Ezio Pinza, and Lily Pons, among others. By joining together, these pioneers hoped to eliminate unfair practices and abuses that were all too prevalent in their profession. Often artists would perform without being paid, or would play out of town and be stranded without transportation back home; rehearsal time was unpaid and there was no limitation on the number of performances an artist could be called upon to give each week. AGMA negotiations came to include pay, terms of employment and workplace conditions, as well as the efforts by the union to promote common aims and interests of the artists, and to foster the musical arts and musical culture in general.

In August 1937, AGMA became an affiliate of the Associated Actors and Artistes of America (known as the 4A's), a federation of AFL-CIO theatrical unions. At that time, the organization merged with an older union, the Grand Opera Artists Association, which previously had held the 4A's charter. In the spring of 1938, AGMA also incorporated the Grand Opera Choral Alliance, an organization that represented opera choristers and had already established a bargaining relationship with the Metropolitan Opera. Thus strengthened, AGMA signed its first collective bargaining agreement with the Metropolitan Opera in August 1938 and became the Met artists' sole bargaining agent.

During the 1940s, AGMA expanded its jurisdiction, negotiating contracts with numerous opera companies throughout the United States. Sick leave and social security benefits were among the goals of the organization, and the union established its own Relief Fund to assist aged and disabled members; the Fund was financed by the Theatre Authority, for many years a clearing house for theatrica benefit performances and other fund-raising. With solid gains having been made in larger opera companies, AGMA turned in the 1950s to the growing field of regional opera as well as to popular professional touring choral groups.

During the 1960s, AGMA was highly visible in lobbying efforts for federal support for the arts, an important feature of both the Kennedy and Johnson administrations. To accommodate performers at the New York World's Fair a "guest status" category was developed and later offered to foreign touring companies like the Moiseyev Dance Company. In 1964 a landmark agreement was negotiated with the Metropolitan Opera guaranteeing 52 weeks for the entire shop. Union contracts were also designed for summer apprentice programs with companies like the Lake George Summer Festival, the Santa Fe Opera, the Chautauqua Institute, and the Central City Festival.

With ballet emerging as a popular entertainment form during the early 1960s, dancers in smaller touring and regional dance companies sought union protection. By the late 1960s the importance of dance to AGMA's jurisdiction was growing, as new dance companies (some representing innovative, non-traditional forms of dance) were being organized in many locales across the country. By the 1980s, ballet dancers comprised about 50 per cent of AGMA's membership and the ballet and dance fields have continued to expand steadily. In 1986 AGMA had 5,500 members, 3,000 of whom were based in New York City. There were ten area offices located throughout the United States, negotiating contracts and handling local problems within their regions. Although AGMA's jurisdiction did not extend to Canada, the association has maintained an office in Toronto to serve as a liaison with Canadian Equity.

Performing arts administration in both opera and dance has becoming increasingly corporate in its outlook and goals in recent years, with less professional theater experience represented in management. By 1990 there were fewer than ten opera companies in the United States that presented more than twelve productions a year; the rest staged from one to six productions.

Membership in AGMA is open to all interested parties, regardless of prior experience, affiliation or nationality. Many performers hold joint membership in other 4As-affiliated unions such as AFTRA, SAG, and Actors' Equity.