The only tracks I enjoyed in the OD rip were Heavens and Partycrasher. All I can say is when you listen to the official soundtracks, you're in for a surprise. A big surprise. Those jazzy songs pale in comparision to the Gungrave game OST: techno, explosive brass with polyrhythm, amazing fusions... Gunlock and Ear Fudge will blow you away. Gungrave Righthead is where Imahori shows he's a great composer: half of the tracks feature a string quartet which plays many styles (funk, trip-hop, ambience à la Silent Hill...), and I tell you, his string work beats his guitar work to shame. The music in Righthead also sounds kind of Mediterranean (four tracks feature mandolin), but there are also a couple of rock themes, and even bebop. It's one of my favourite soundtracks ever. You'll fall in love with "The Maverick", "B. G.", and "Family" the moment you listen to them.
Lefthead features more electronic music (but there's still some rock, and an off-beat waltz with marimba and sax). "Gunlock Overdrive" (remix of "Gunlock" from the game OST), "I Want to Be Free" and the Kanno-esque "Dr. None". Overall, it's not as good as Righthead, but still one million times better than the OD rip. Those tracks were left out of the soundtracks for a reason.