The Sound of Music was a musical. Julie Andrews was an actress in the film version of the musical.
Sylvia Gribbins thought that St Agnes Abbey was "a long way off anything in The Sound of Music" and the nuns didn't remind her much of Julie Andrews, either. (PROSE: Eye of the Gorgon)
The Fifth Doctor saw The Sound of Music at Christmas on TV. (PROSE: In the TARDIS: Christmas Day)
Behind the scenes Edit
According to Russell T Davies, David Tennant went to the theatre with Kylie Minogue, to see The Sound of Music. He wondered why this didn't make the tabloids. (The Writer's Tale)