The term EXTRA IN 'THE SOUND OF MUSIC' is solved by the 3-letter word NUN. The Sound of Music is a classic musical film released in 1965, starring Julie Andrews as Maria, a young NUN who leaves her convent to become a governess for the seven children of a widowed Austrian naval captain. The extra in the movie is the character of Sister Margaretta, a NUN at the Nonnberg Abbey who helps Maria and the children escape from the Nazis.