Callas is known for her distinct voice. She was a versatile singer, with a large, penetrating voice. But, for all its power and range, it wasn't for everyone. Her style was off-putting to some conventional opera fans, and many music critics acknowledge her shaky high nights and “bottled” sound. “When you interpret a role, you have to have a thousand colors to portray happiness, joy, sorrow, fear,” she is quoted saying in Callas : The Art and the Life. “How can you do this with only a beautiful voice?”

Not only was Maria known for her unique voice, but her acting skills as well, which are on display in the clip of her performing “Vissi D'Arte” from Tosca, above.

Callas discussed her reputation for being difficult with Mike Wallace on 60 Minutes in 1973, including the largely exaggerated story of her “walkout” on a 1958 performance in Rome. Whether you call it “difficult” or “temperamental,” some might say it's inspiring to see an artist bold enough to assert herself the way Madame Callas had. (You can see part two of Wallace's interview here.)

Playwright Terrence McNally wrote two plays inspired by Callas. The first, The Lisbon Traviata, centered around a rare recording of a real 1958 Callas performance in Portugal and relationships between a group of gay men. He also wrote Master Class, which told the story of Callas teaching at Juilliard in the early ‘70s. You can see Tyne Daly as Callas above, but the role was also performed by other gay icons Dixie Carter, Patti LuPone and Faye Dunaway (who has been working on a film adaption of the play for years).