Define a Dance Film

When defining a genre one must look at the type of film it is-is it a contemporary or mainstream?
Then we start to look at audiences. What age is it aimed at? Is it a 'youth film'?
According to Roy Stafford however, defining genre is impossible as 'genres are not fixed or static-they change over time' This change is exactly what i want to look at and how our perspective of dance films have changed and coincided with other sub genres e.g. the difference between the 'moral panic' of Dirty Dancing's exposure film to Silver Linings Playbook. Both were distributed as Indie romances aimed at an older female audience but the theme of dance it heavily weighted on Dirty Dancing through the majority of the film compared to the last hour or so of Silver Linings Playbook. So is it dependant on theme?
If so, the classic musical Hairspray has the whole cast dancing and singing with a protagonist obsessed with dancing but that isn't counted as a dance film in comparison to the Step Up franchise. And so the struggle to define a dance film continues.
The audience for these films varies depending on the individal movies but as a whole the 'dance film genre' is aimed at the youth audience, teaching them an escape from reality and rebelling against social conventions for the greater good but is always misunderstood reflecting teenage attitudes and conventions in order to reach the target audience.
The reason the audience varies however, is with classic films such as Footloose and Dirty Dancing (although Footloose had a remake in 2012 and Dirty Dancing rumors of Kenny Ortega directing a remake) because it's original audience was 80's born therefore hits an older audience today.
Additionally films such as Mamma Mia and the new current release hit the more older audiences due to the music content of the 80's and generally having an older target feel through themes of marriage, motherhood and affairs that appeal to all female audiences alike through the genre of a comedy.
Personally I find these listed films (Mamma Mia,Walking On Sunshine) more in the musical genre because of the singing characters content. But then, what can be argued about Baby and Johnny lip syncing to Love Is Strange. Does that count as singing therefore the verge of a musical? What defines a musical from another genre such as musicals or in Black Swan's case, thriller genre?
Again like Mamma Mia, Dirty Dancing and Hairspray the films look at themes such as family/motherhood/mother-daughter relationships, implied sexuality and relationships. As does Black Swan. So can we define genre through themes? Are all these dance films? Is the audience purely female? The answer is no, the explicit imagery in Black Swan and the thriller genre opens up audiences to the male audience using the likes of Natalie Portman and Mila Kunis with the famous 'lesbian scene' that turns out to be Nina's hallucination arising the question of how far is too far in the dance film genre and is it really necessary?  
So the question is WHO is the audience for dance films? Typically, it is teenage girls where the idea of rebellion and the rebel would appeal; however as the films look at mother/daughter relationships it additionally aims at the older female adult audience.