The score was done by RZA and Howard Drossin... this instrumental set has been the best study music I have possibly ever found, so check out The Man With the Iron Fists (Original Motion Picture Score) (on Spotify).
More glorious however, is the actual soundtrack. With a ton of talented lyricists and amazing production, RZA has created a masterpiece. The only thing missing is the actual movie. I will be playing my favorites tonight, but here is the whole thing:
A song by the Wu-Tang Clan as a whole again?! And they even performed it live on Jimmy Fallon: