Other mistake: When Rocco taunts the Russians he is punched in the face, yet he continues talking in a steady tone, and finishes his joke while falling into the bar. (00:20:39)
Other mistake: In the scene where the brothers are going to kill the "fag man", the fourth man has his shoulders perpendicular to the brothers in the center of the room but the bullet goes straight through his chest. The shot wasn't even at a close enough angle to go through his chest like that. (00:40:35)
Other mistake: In the scene when the brother is calling the number on the Russian's pager, he writes down the name of the hotel before you hear the Russian say the name over the phone.
Other mistake: The brothers executed the "Fag Man" by crossing their guns and the bullets coming out of opposing eyes. You can see when they show the flashback of the execution that the guns are held at nowhere near enough of an angle for the bullets to cross and come out the eyes.
Other mistake: In the scene where Connor and Murphy are waiting to hear from Rocco, the phone rings with an "electronic" style ringer, yet when Murphy quickly picks up the phone you hear the sound effect of a mechanical bell being jarred. The same bell is heard when he hangs it back up. (00:54:00)
Other mistake: In the scene at the bar when the Russian gangsters arrive, Ivan speaks with a heavy Russian accent. In the scene directly after the bar fight, after he kicks in the door to the apartment, Ivan yells his first 4 lines with no accent. (00:07:20 - 00:20:40)
Other mistake: When Paul Smecker tells Detective Dolly: "Well, now that Duffy's relinquished his King Bonehead crown, I see we have a new heir to the throne," "throne" is misspelled on the DVD subtitles as "thrown."
Answer: The song is titled "Indigino" it's a foreign techno song by "The Chidros".