There are two distinct musical threads in the soundtrack of Birdman, Alejandro González Iñárritu's earnest film about a middle-aged actor's existential Waterloo. The drama is supported by a dozen choice cuts of classical music and a smattering of original stuff, notably from a jazz drummer (of which more later).
First to the classical library. To get Riggan's internal drama out onto the screen, Iñárritu uses a dozen or so late 19th century romantic scores; rich, expressive, mature music for the epic struggle going on inside a man who want to make good an imperfect life. Tchaikovsky is perhaps the most readily identifiable of in this respect, music that is synonymous with the theatre. The director uses excerpts from both the fourth and fifth symphonies (here's the fifth, complete)
It was interesting to me that the music with the most overt psychological narrative, two works of Gustav Mahler, were used early on. This is because the opening of the Mahler's 9th symphony and one of the five-song set of Rückert-Lieder deal directly with issues of mortality and life-satisfaction. I particularly liked the second iteration of the opening of the 9th symphony in the film (at the opening of this complete recording): it occurs as two characters stand beside thick ropes hanging from the theatre flies, which look like the resonant harp strings we can hear plucked in the score, evoking Mahler's temperamental heartbeart.
For all that Birdman is a Big-Apple-paced comedy at heart, there's no questioning the seriousness of Iñárritu's intent when we hear the opening of the song Ich bin der Welt abhanden gekommen from the Rückert Lieder:
I am lost to the world
with which I used to waste so much time,
It has heard nothing from me for so long
that it may very well believe that I am dead!
Later on Keaton's Riggan indulges the tempting suggestions of his fantasy alter ego after a night on the tiles. An explosive 30 seconds of generic blockbuster boredom gives way to a more peaceful, magic-realist sequence that is underscored with Rachmaninov's 2nd symphony, high-watershed heart-on-sleeve Russian soul-baring music.
Interestingly, I didn't readily identify the excerpts of Ravel nor those of John Adams - which included music from Adams' opera The Death of Klinghoffer which was itself the subject of Broadway controversy only this year.
The second of Iñárritu's choices involves music that is more than just soundtrack. The musician Antonio Sanchez was invited to produce an original score on a drum kit alone. This excellent, organic character-in-sound (surely the most two-dimensional musical addition to a film since There Will Be Blood?) pops up throughout the film.
There is a nice account of the process in this Vanity Fair article. It was especially powerful in a film that was preceded by a trailer for Whiplash. Further information on original music written for the film by Joan Valent & Victor Stumpfhauser can be found on the Birdman IMDb soundtrack page.
(Excerpts on this page may not be the actual performances used in the film)