Some of the best game music is normally, no not the tunes from the games themselves (maybe on occassion since the medium has gotten much better during the 16 or 32 bit era) but from arranged music by various bands.
Instead of doing a top 10, I'm just going to be listing various bands and what music they've done in the past. In the past it used to neccessary to import CDs from various web sites or mail order (many web sites I had bought from are now gone to the big internet in the Sky), but now Amazon has been a great place to listen and buy what you like one tune at a time!
S.S.T. Band: (check wikipedia on their history)
This band goes way back to nearly 1988 and arranged some of Sega most well known game tunes from Outrun, Afterburner and Space Harrier among others.
Black Mages: This group's rock/metal style has completely revamped the Final Fantasy music we've all grown to love, from 1 to 7, to 9 and even 11. Not all of it is hard rock. They've made a total of 3 albums so far.
Distant Worlds: I & II
Artie(Arnie?) Roth (known for his help with Chip Davis and the Mannheim Steamroller) directs the symphony that performs these works also from the Final Fantasy games, including the joke opera "Darkness and Light" from Final Fantasy VI. They have recorded 2 CD albums. They toured the US and some of Japan I believe also.
We Are Error
A rock band with a sound not to dissimilar from many old hard rock bands like AC/DC or Metallica. So far I know of only album(CD) they've made "Year 200X". They do utilize some acoustic sounds also. Their Zelda II medley is to DIE for! They build up using music from both original NES Zelda games and peak using the dungeon tune from Zelda II which is some amazing simply fast arppeggio guitar work using 16th notes against quarter note triplet! The counterpoint is very clean and emmaculate.
Daniel Tidwell (Versus Video Games)
Daniel's music is really superb. I really like his style. Again all instrumental rock-gaming goodness. The pentatonic acoustic lead and ending in "The Winds of 600 AD" (which is the main theme) explodes into an awesome rock melody. He always knows just when to back off. Super Duper Mario... not one of favorites actually. His "Over the World of Hyrule" is very good. It starts off NES perfect in the acoustic style and again turns into a powerful rock melody that only he can do. His instrumental mixing is perfect every time even on tracks that "aren't as good".
Retro Remix Revue 1 & 2
I don't much of thier stuff, but what I have is very enjoyable. "Sonic the Hedgehog - Green Hill Zone"... no one else can even touch how well they arranged the original Sonic theme. They handle Ken's Theme from Street Fighter II just as easily. And Sonic 2's Chemical Plant Zone is another masterpiece. They could make a CD of nothing but Sonic arrangements I bet. But we can't overlook their "Castlevania III: Beginning" either. Love the theme, and what they did with, very close to Jack Wall's rendition.
The Advantage (Elf Titled)
Their selection is smaller, but still fairly well done. Mega Man's Stage Select & Metal Man fit perfectly. Kraid's Lair is...eh ok. It's grown on me. Ducktails - Moon... it seems like everyone has done this one... and like most of their instrumental work of game arrangements... most of their music is easier on the ears compared to Tidwell or We are Error. Their style is much more laid back. So listening to their arrangements of their Castlevania music is very satistfying to listen. Oh, "Wizards & Warriors: Tree Trunk" is an odd but neat arrangement. It's as funky as the original game music, but they do the "chant" near the middle... it is so..wierd, but yet so cool at the same time... not sure why it took them 1 minute and 30 seconds more just to fade out... but hey... like I mentioned it IS odd. (just skip to the next track once you start hearing the repeated octaves... bouncing from left to the right channels over and over...and over...
The Oneups (Volume 1 & 2)
I don't many tracks of these guys either, AND they've made a 3rd game arrangement CD earlier this year I just found out about too. Andy Asteroid
Mario & Zelda Big Band Live CD (import 2003)
Video Games Live (CD) (2 CDs)
It's Time for Revenge...Let's Attack Aggressively
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