Nothing earth-shattering, just something I've been wondering about.
A while back, I treated my Mom & Dad to a revival showing of "Buck Privates", the classic comedy with Abbott & Costello. The unusual thing is that the showing was part of a weekend of movie musicals. Now, you normally wouldn't consider "Buck Privates" a musical, but, by my count, there are seven actual musical numbers in the movie, with two performed by major characters as part of the plot.
So, in your opinion, what exactly qualifies a movie to be considered a "musical"?

