The organ portion of it sounds like "Come, Sweet Death" by J.S. Bach. But the whole score of the film except for two songs is written by James Newton Howard. The song you refer to is called 57th Street, but who knows how Howard came to write it... he might have used another piece underneath and worked on top of that, as score-writers often do. So if he did, my guess is that he elaborated on "Come, Sweet Death." But I may be wrong.

Besides, they did use Bach's organ music in another part, which is credited to Virgil Fox, a famous organist. The track right after 57th Street is Air on G String, which is undeniably by Bach, no matter what they say. But maybe Virgil Fox arranged it and that's what they mean by crediting it to him...

So you see... if they did that with that piece, then maybe the same thing happened here; maybe Howard just arranged and elaborated on another piece and called it his own, as well.

I could be wrong, but that's my guess. Let me know if you find out anything more, I'm intrigued. JustMe would probably be of invaluable help as well.