Pete, the IMDB says this:

"In the shot in which Alfred Hitchcock's cameo occurs, the music briefly changes to "Funeral March of a Marionette" by Charles Gounod, which is best known as the main theme for Alfred Hitchcock Presents."

That well-known dum-de-duh-duh-de-dum-de-duh was just inserted into the background music, which was a Strauss waltz. Lorna's answer is correct.