Professional musicians organized societies to protect their jobs when traveling bands, touring foreign musicians, and technological broadcasting and reproduction developments created shortages in available local work. In 1896, musicians organized the American Federation of Musicians, a national union affiliated with the American Federation of Labor. By 1943, almost all professional conductors and instrumental musicians in the country had joined the union. The union insisted that traveling members could not perform without a local house orchestra or the union’s consent. Gamble Enterprises, Inc. (defendant) owned the Palace Theatre in Akron, Ohio. Until about 1940, the Palace employed a pit orchestra of nine musicians that played for vaudeville stage acts and sometimes with traveling bands. When the Palace switched to showing movies with only occasional traveling-band appearances, the local musicians remained available but no longer played on a regular basis. The Palace nonetheless paid the orchestra minimum union wages each time a traveling band appeared, even though the orchestra played no music. Congress passed the Taft-Hartley Act in 1947, prohibiting unions from demanding standby pay, and the Palace stopped paying it. Seven traveling bands appeared without local musicians, who did not object or demand standby pay. Instead, the union proposed that the Palace employ a local orchestra to play overtures and intermissions during traveling-band performances, plus chasers while patrons left the theater. The Palace refused, and a traveling band canceled a scheduled performance because the union had not consented to playing without local musicians. The union continued to block band appearances for the next two years, but the parties could not agree on the number of performances for which the theater had to employ local musicians. When the Palace filed unfair-labor-practice charges against the union, the National Labor Relations Board (NLRB) (plaintiff) dismissed the complaint, but the appellate court reversed and found the union engaged in unfair labor practices. The Supreme Court granted review.