Rockstar's soundtrack supervisor Ivan Pavlovich spoke with Rolling Stone to finally reveal what we can expect out of the soundtrack. There's going to about "20 movies worth of score" featured in the game comprised of 240 licensed songs, 15 radio stations, and two talk radio stations.
Rolling Stone's article also has a ton of samples straight from the game of how some of the stations will sound like. There's a Mexican, pop, classics, 80s funk, classic rock, and way more stations you can expect.
Plus on top of all this is the original score that was done for GTA V, a first for the series in fact. I heard some of these songs when I went to check out the game and it sounds so good. It helps that Woody Jackson, who scored Red Dead Redemption and L.A. Noire, did some of the original songs here too.
Inside the 'Grand Theft Auto V' Soundtrack [Rolling Stone]