Well, like some people here, I made an account to be able to talk about soundtracks I imagine you would like, Ross.
I'll go from a list of soundtracks from games that I think have really great soundtracks.
Okay, to start it off, this isn't a game as much as an absolute SERIES, a massive massive indie series in Japan. But if there's one thing about it I love, it's the soundtracks.
Touhou has incredibly good soundtracks, all composed by the creator of the series, ZUN. And I think the Touhou games have great soundtracks.
There's a lot of games, but the fighting games of the series have some really wonderful songs, but the songs in the main series have good music too.
A list of the official soundtracks from a fan site
And the soundtracks of the spinoff games are good too
On the same fansite as well
These are locations to download the soundtracks, since you can't really purchase the soundtracks, but they are really great soundtracks.
And another game with a great soundtrack is a game called Rimworld. Rimworld is a sci-fi colony management game with cowboy western-like elements all over, and the soundtrack embodies a lot of western-styled music, but all of the songs are a very nice listen.
And another game with an underrated soundtrack is from a game called Cortex Command, which is a side-scroller base management sci-fi almost RTS-styled, thing. It's been in development for a very long time, and the way the game is put together can almost be considered a mess due to how the game has been made for so long, but it's a very enjoyable game. And it's soundtrack is so slouch either, in fact some people consider the soundtrack better than the game itself, but I enjoy both. But the soundtrack is really great, even if there isn't THAT much of it.
Again, Youtube playlist but I haven't found a place to buy the soundtrack
Another game with a pretty good (and interesting way to handle it) soundtrack is a game called Luftrausers, which is a 2D arcade-style aerial combat game. And the game handles the soundtrack in an interesting way, because in the game, you can change your plane and the soundtrack changes with your plane from a set of different ways and it's done pretty well. Oh and the soundtrack is purchasable off of Bandcamp.
And one last game with a really good soundtrack is called World of Goo, and World of Goo is an indie puzzle game involving the use of goo balls. And the game itself is very fun, but the soundtrack really sells it. The soundtrack is pretty damn incredible and the creator, Kyle Gabler, even allows it to be downloaded for free.
Downloadable here, even with amusing track notes
So that's all I have to give for now in terms of game soundtracks, all from indie games when I look back on it, but hell, they all got great soundtracks, and I just felt the need to share it with you, Ross, and perhaps anyone else stumbling upon these songs.