Cho Ren Sha 68k has a really sweet soundtrack. I think one might appreciate it more if they played the game a bit, since the way the levels and songs are designed they sync up with what's happening on-screen exceptionally well. I'm refraining from listening to the entirety of it since I haven't beaten the game and getting to a new level and hearing its song is like some kind of exciting new reward for me.
The songs sometimes mellow out a tad or change tone on the later levels, like here:
I'm pretty sure the soundtrack was for sale at some point but I don't know if it's free to download or not. I'm pretty sure the guy who made it lets you stream it on his website or something.
The game is also freeware if anyone wants to play the actual game. It's a shmup, but it's pretty accessible and doesn't do any bullet-hell type stuff. Generally you can blow up enemies before they start firing off, and it's pretty easy to get the hang of (especially when you learn you can pick up all three power-ups at the same time).