The Lancashire Evening Post, a local British newspaper, has posted an article on its website about a singer-songwriter called Kurgan Merrick (not his real name). While at first he seems like a bit of an egotist, interestingly he claims he has been contacted by Rockstar and asked if one of his songs could be used in Grand Theft Auto IV.
"I was contacted by someone who has heard my songs on the website. They wanted a track they could use on the car radio as people are driving round the game."
Merrick describes his style of music as "synthesiser music with samples and heavy guitars". Rockstar are remaining tight-lipped about any details regarding the game, so again we we have no confirmation on whether or not he will feature in GTA4. You can visit his website for some samples of his music.
This isn't the first rumour we've heard regarding soundtrack details, the first appeared as a topic on a forum (which was promptly removed) where 80's New York-based band Breakdown were allegedly contacted by Rockstar Games.
If both these rumours turn out to be true it seems like we'll be hearing quite a few different types of music in the game, just as we have in previous iterations.
Thanks to gta4.net for the heads up.