Just a few days ago I wrote, "The new voice emotes will give me more of a reason to play with the game sound down and Winamp sound up." But perhaps I will no longer have a need to lag myself by running extra progams.
Yes, Live Update 9 (part of which is currently on Test) will allow you to listen to custom music while playing EQII. I know some people will say this feature should have been available from day one but I'm just glad it's on the way.
I don't want to beat up on the people who created the original EQII music. It's good. I remember being impressed the first time I heard the drums in Blackburrow and the soaring tunes of Antonica. It just gets repetitive. Especially for those of us who play a great deal, custom music will be a welcome change. An ingame mp3 player would be great, but this system will satisfy me for now.
I know some people listen to music on their iPods or PSP's while playing, but then you lose out on other game sounds.
If you're looking for some ideas on what music to listen to during an EQII session you can check out this thread from the official forums.
Forum member Jowana did put together a well received music pack based on Lineage II music but due to copyright issues it was removed from the official forums. However, it does appear to be available elsewhere. (edit: Sorry, the actual download link appears to be down).
Edit: While we're on a musical note, Van Hemlock has a review of the online EQ2 radio show up on his site.
I personally like to listen to orchestral or new age type music when playing, with some occasional indy rock mixed it.
As for how you get your music that's a bit beyond my ken. I will mention that downloading songs from Kazaa is both illegal and a good way to get a lot of viruses. Yahoo recently unveiled a music rental service to compete with Napster's. It is reasonably priced at $4.99 to $6.99 a month (based on whether you buy a monthly or annual subscription). More info here. There's also iTunes if you like to own your music and don't mind spending some cash. If you like to live on the edge, you can try AllOfMP3, a Russian based site which offers outrageously cheap downloads (in the neighborhood of pennies per song). But the legality of this site is very questionable so I can't really reccommend it. Of course, there are plenty of free programs available that will let you burn your existing CD collection into mp3 files.
Speaking of music, if you haven't yet seen this a capella rendition of Nintendo themes which has been floating around now is your chance to check it out.
Another feature of the next Live Update which I will mention briefly is the introduction of solo guild writs for levels 45 and up. Hopefully this will turn out to be a useful way to pass the time (in addition to tradeskilling or harvesting) while waiting for guild groups to assemble.
There is also this news from the Update notes: "It no longer rains underwater."
There's a joke to be made there I'm sure but you're on your own. I have to go organize my music collection.