Dangun Feveron by Cave, 1998. Yeah, so Cave's made some pretty popular shooters, all with crazy names which I can't remember (Battle Garegga - wasn't that them?) Lots of the "bullet hell" variety, whether or not that floats your boat. It usually doesn't do it for me - but Dangun Feveron is definitely an exception.
So, what we have here is a vert shmup with a Disco theme, these kinda things usually veer more towards techno or what-have-you. It's an odd departure, but a nice one and well-handled. I mean, don't get me wrong, it's goofy as al-get-out but it certainly makes this memorable (and yeah, it does sound pretty good!) Check out the YouTube if you are so inclined.
Pretty standard stuff besides. Rock-solid visuals with enjoyable "blast 'em and survive" gameplay, you need to "rescue" little floating disco dancers (in colored balls) as you blaze across the galaxy for the BIG POINTS. Charming. The firing system is interesting as well - you can hold down for a steady stream, or tap the button for more burst-firing but increased manueverability. It's your call, but make sure you employ the proper method appropriate to the situation or else you'll be toast.
Though I am a pretty big shmup-fan, these late-games aren't usually my thing - but this one is a good find. It is playable on MAME, otherwise I am sure you could book yourself a flight to Japan and find one still sitting in an arcade somewhere...