Hi, Senior. TMDb's rule is that solely something like a music concert or music documentary is to get a "Music" genre designation. For movie musicals and the such, add "musical" to a film's keywords list, if it doesn't already appear there. (For this movie, it already does.) If you then click on the musical keyword that's been added there, it'll take you to a list that includes that musical movie (or musical tv special, etc.) as well as many, many others.