I got hired to work on a shmup kind of recently and I don't really know much about shmup music so I began digging around. I discovered this one company called Toaplan that released like 10 games, but every single game they released had a super good soundtrack - the one you're most likely to be familiar with is Zero Wing. Toaplan split up, but most of the people went on to work for Cave, which is pretty much the biggest name in shmups. The one soundtrack that really blew me away was for a game called Vimana, a shmup that's apparently based off of Hinduism or something? ??? ?? It was done by Toshiaki Tomizawa, one of the founders of Cave, and it's nuts!!
Space HighThis is my favorite song in the game, although all the songs are pretty similar to this; this sort of Hi-NRG/Italo disco/game music hybrid. Here's another one:
The Power of DarknessHere's the whole album. The album comes with the music from another game, Teki Paki, but it's pretty terrible so just stick with Vimana. Check it out, it's pretty wild. Actually, search for Toaplan on Youtube because everything they did is super good.
Also I don't know if it's actually from a game or not, but
this Atari ST song I found recently is nuts. Actually I can't remember, maybe Ragnar posted this song.