We've had a number of Questions of the Week along these lines on the Discord, but I wanted to expand on that a bit more with a post specifically focusing on great music that doesn't come from the usual suspects. So here are 10 video game music people who don't typically show up on these lists, along with some examples of their music that often also doesn't fit into typical video game fare. There's no Uematsu, Fox, or Wise here, but hopefully you'll still find something new to appreciate.
bLiND doesn't really count as an underappreciated pick to anyone who follows OCRemix closely, but since that's a small minority of gamers, you can be a big name there and still largely unknown everywhere else. I've linked one track from the recent Tanknarok OST that nails that game's arcade chaos feel and a second, significantly older track remixing the "Auckland" theme from the SNES's Top Gear 2.
It won't be a surprise to anyone who has heard me talk about games in the last year that Like a Dragon is making an appearance here, but its OST has plenty of twists and turns to make up for that. LaD makes use of a mix of rock and dubstep for its boss battles, which at the latter extreme is about as far as you can get from typical RPG fare. Oh, and it's only natural that he's also responsible for Super Monkey Ball 2's bizarrely intense OST. "Monkey Dogfight" sets the mood for a bunch of monkeys who apparently read the Icarus myth to shoot pineapples at each other, but it'd work just as well as a boss theme in a much more serious game.
As far as I can tell, COIL only ever made this soundtrack in the VGM space, but it's hard to tell since they share their name with a better-known British band. Regardless of whether there's anything else out there, this is a masterpiece of variety. "Born to be Bone" is my favorite, perfectly communicating the very specific feeling of a dance shootout with a band of mariachi skeletons. But never fear if you're worried that that's all they could do: "Flyin' to your Heart" shows they're equally adept at making Eurobeat by which to defeat aliens in a roller blade challenge.
Gitaroo Man is a weird game.
No list of mine could be complete without Zero Escape sneaking on somehow. Its OST isn't always the most listenable on its own since most of it is meant to take a back seat to cutscene dialogue, but Hosoe's music still delivers when it's time for the puzzles to take center stage. And while Zero Escape offers plenty of material to work with, Hosoe isn't limited to making music for good games - Giga Wrecker is a mess, but he was somehow still able to find inspiration in it for the absolute banger that is "Dragon of the Diamond Cave."
Garoad is one of those composers that's immediately recognizable from almost any track. This sort of upbeat chiptune-jazz-thing is impressive enough to listen to on its own, but I think making it work in a horror game like Yuppie Psycho deserves a lot of extra credit. VA-11 HALL-A was a perfect game to feature this music since it had an in-game jukebox that let you set your own tracks each day.
Jeff van Dyck
I first noticed Jeff van Dyck's name on the Assault Android Cactus OST, which is, as you'd expect from a twin stick robot shooter, mostly electronic and rock music. It's perfect for that game, but it wasn't until I later noticed that van Dyck also composed the soundtracks for Fall of the Samurai and Emperor: Rise of the Middle Kingdom that I really appreciated his range. These OSTs don't even come close to sharing any instruments or a mood, but they're from the same person and both fit perfectly into their genres. How many people out there have written both dance and classical Chinese music?
Miracle of Sound (Gavin Dunne)
You might argue that this is cheating since neither of the songs I posted are actually part of the associated game, but MoS has written music directly for games and his work is so strongly associated with the games in my mind that it absolutely counts for me. He can work in seemingly just about any genre, and in doing so often creates tracks that I enjoy more than anything on the real OST. Picking two representative songs was hard, but I went with "The Great Unknown", which could fool you into thinking Mass Effect: Andromeda is worth your time, and "Mojave Song", an 8-minute epic that covers all of Fallout: New Vegas.