This is in early access at the moment, though it's pretty dang good already. Only 15 songs right now, but it's a varied and good selection (IMO). It's perfectly playable with M&K (not sure how it plays with a controller), but it also has support for MIDI devices (like DJ controllers):
I played through Spooky Ghosts Dot Com, a little Metroidvania that comes in under two hours. It was fine, the premise and stylings are attractive even if the quality of the art is middling and severely lacking in animation (enemies and even bosses having no death animation, just disappearing on death, would be one of my biggest criticisms of the game!). There wasn't much in the way of new moves - only a charge attack that can destroy walls and an airdash that grants invincibility. The other upgrades were health increases, extended iframes, and then an over-reliance on keys to gate off progress, so it fails on that major aspect of metroidvania. It did however have some relatively fun bosses, the difficulty curve was about right, and it never outstayed its welcome. Not a bad way to pass an hour or two if you pick it up in a sale I reckon.
A few of us got to together last night for a Games Night which was a lot of fun. We played a few rounds of Towerfall which went down well. We also played a game called Crawl which was really interesting and also really good, it seems to take around 30-40 mins to do a complete match so it’s more in depth than other multiplayer games.