The Symphony Six were a group of Canadian musicians under contract to the Toronto Symphony Orchestra (TSO) who were denied entry to the United States for a concert tour in November 1951. Coming at the height of the McCarthy era in the US, the six musicians – Ruth Budd, Dirk Keetbaas, William Kuinka, Abe Mannheim, John Moskalyk, and Steven Staryk – were denied visas on the suspicion of being involved in communist activities. The TSO sent other musicians in their place and completed its tour. The six musicians resumed playing with the orchestra upon its return to Canada.
At the end of the 1951-1952 season, the TSO refused to renew the contracts of these musicians, stating that they had not fulfilled their contractual agreements. The six musicians appealed this decision to its union, the Toronto Musicians' Association; the Mayor of Toronto; the Canadian Civil Liberties Association; and many other bodies, without success. They received support from the Federation of Canadian Artists and the Canada Council for the Arts, but not from the Canadian Congress of Labour. The incident garnered extensive media coverage in both Canada and the United States, and sparked a protest against the TSO's decision. The orchestra's director, Ernest MacMillan, did not speak about the matter in public, which also prompted criticism, and two members of the TSO board resigned. The six musicians were viewed with suspicion by their colleagues and people avoided them to protect themselves from guilt by association. Budd and Staryk later returned to the TSO, while the four other musicians continued their careers elsewhere.