I can't express how happy I was when you asked us for game Soundtracks.
I'll share this link where you can get the full "Shin Megami Tensei IV" Soundtrack (http://mass-destruction.tumblr.com/SMT-Music) along with all the other SMT saga soundtracks.
SMT IV has one of the greatest, longest and marvelous soundtracks I've ever heard in any game, you probably won't play it (it's a 3DS exclusive) but the Soundtrack is a MUST LISTEN.
I recommend this tracks:
-Main Theme
-Ikebukuro Underground District
-Challenge Quest B
-Battle - b8
But I know you will enjoy the full soundtrack.
Also, check out the SMT Devil Summoner: Soul Hackers Soundtrack, that thing is rad.