(Inside joke) When asked to play without music, Prof. Magenbruch (Benny Goodman) says, "You can't play without music." The others answer, "Well, Benny Goodman used to." Magenbruch then says he's never heard of Benny Goodman.
In 1948, when "A Song Is Born" was released, the American Federation of Musicians was striking the record companies and union musicians could not legally make records. Nonetheless, the union allowed Capitol Records to make an album of music from the film because the company agreed to donate the proceeds to the Damon Runyon Cancer Fund, In the year between the film shooting and the recording sessions, Benny Goodman had radically changed the personnel of his band - notably adding two bebop musicians, trumpeter Theodore "Fats" Navarro and tenor saxophonist Wardell Gray - so the version of "Stealin' Apples" on the record doesn't sound at all like the one heard in the movie.