Freq Fire is curious. It plays like a fairly derivative vertically scrolling shmup. It looks OK. It throws waves of enemies at you in unimaginative patterns. There are powerups.
It's got a musical motif though. Powerups arrive the shape of musical notes and signatures. And when you start a new game it asks for your favourite band. It then pulls a random song preview of that band from Amazon, then pulls more random songs from similar artists, again from Amazon previews.
Which is nice, I guess. You're stuck with whatever's on Amazon, so if your taste in music inclines towards the obscure then you may be a little disappointed. It's no Audiosurf, obviously, but it's a decent enough way to pass a few minutes.
Freq Fire [Kongregate]