If you leave the game on pause for at least 45 seconds or so, the song builds to a really, really cool beat. I've actually really become addicted to it. If you're curious, give it a shot.

I'll totally have to check this out. Thanks for the heads up, man.

hey i totally agree, must find mp3 & put drums to it!

is it the same as the music they been playing on the trailers?

I'll assume you mean in BOGT. Yes it's louder in BOGT than TLAD or GTA4. The cool thing is that it's up to three ambient tunes at a time randomly assigned to one of the sound channels each, which sounds trippy in dolby surround. For example you'l hear the beat in the rear left, the synth in the front center, and the vocals in the front right. Then they'll each fade to another speaker.
 
It's just a tune that plays as the theme song for the episode. Presumably it'll play in full form when you beat the game like the ones in TLAD and GTA4 pause screens (not sure as I havent finished it yet).