UT's music styles was DEFINITELY the perfect fit, and one of the reasons I absolutely love the game. Each map's music fit like the pants of a man with five penises - like a glove.
2003's mostly sucked, there were a few good ones, though 85% of them were Starsky Partridge's LevelXX series.
2004 had some better ones, with Rankin having a distinct 99 feel to it. Ideally, all the UT99 Music Guys (Van Den Bos, Brandon, et. al) should team up with Kevin Riepl and Starsky Partridge, to make the ultimate soundtrack.
Sound is one way to immerse someone into a game, into the little virtual world you create, and if you get the mood right, they will completely suspend Disbelief. All you oldtimers out there who play with music on, all I have to do is say "CTF-Face" and that familiar tune of Foregone Destruction should start playing in your head. Likewise for CTF-Lavagiant's Skyward Fire.
Which was another good thing about UT's music... variety. It had plenty of Adrenaline-raising stuff (Razor-UB anyone?) but then had calmer fare like Skyward Fire and Foregone Destruction. It completely set the mood, perfectly, and far better then both 2003 or 2004 did (Though 2004 also has some good ones - ONS-Dria's fits PERFECTLY.)
To this day, I play with music on, despite my peers looking at me like I have a disease. Sorry, but I like the music a lot, and I seriously hope Envy has a kickass soundtrack, one right up there with 99's.
Please don't disappoint, Epic.