The Greek letter mu is used in physics notation to represent the coefficient of friction—and accordingly, this wacky and brainy crew could have hardly chosen a more relatable handle. The name seems to conflict with inventor Nikola Tesla's famous concept of free (i.e. all-natural) energy, but the clash is pretty apt for Free Energy!, which revels in such craziness. The friction they create comes from wildly mashing up a few stylistic elements that aren't always known for compatibility—in large part it's a mix of jazz-rock fusion, avant-garde weirdness and '80s Britpop. You can't always dance or trip out to it, but free and (almost always) full of energy it certainly is.

This Polish quintet bases the album around song forms, often with actual verses and choruses, but they're also willing to interrupt them with off-the-wall noise, and name one rambly fusion piece after