Chaotic. That's how I describe the protagonist's mind. The music suggested a very active mind, coupled with that raspy voice egging him along. The ever narrowing and darkening corridors of the theatre were closing in on him just before he hit the stage. After all, the hero of the movie was a has-been. He was an actor who's claim to fame was his stint as the superhero character Birdman.
Of course there's some humour underneath the surface. Michael Keaton, in no way a has-been, used to play another winged superhero, Batman. I'm sure that the Bat's not haunting him straight to the theatre though. Other characters were portrayed by actors who were castmembers of other superhero movies too.
What's blindingly obvious was the absence of the castmembers of The Avengers franchise; so, the Avengers themselves made a cameo. Hahaha!
The way the movie ended still has me baffled. Did he or did he not... Fly? To me, this ending is akin to Inception's spinning top. I'd say...
Nah. I need to watch Birdman again before I can claim that I've understood the ending.