用英语，简单地概括出电影“音乐之声”的大意吧

In Salzburg, Austria, Maria, is studying to become a nun and she was sent from her abbey to be the governess to seven children of a widower naval commander, Captain Georg Ritter von Trapp.

The children, mischievous and initially hostile to Maria, eventually come to love her when she introduces them to the pleasures of music and singing.

The Third Reich takes power in Austria as part of the Anschluss and tries to force Captain von Trapp back into military service. The Captain, unwilling to serve the Reich, delays the matter by insisting to Zeller, the Gauleiter, or party leader for the district, that he is part of the Trapp Family Singers and must appear with them during a performance at the Salzburg Music Festival, in a guarded theater. The story ends with the von Trapps hiking over the Alps to Switzerland.