PUZZLEAlthough emo is often thought of as a direct descendent of punk and alternative, the genre's tricky song structures oftentimes teeter toward prog territory. Case in point: Puzzle, the fourth full length by Ayrshire, Scotland's favorite sons, Biffy Clyro. While the riffs and singalong choruses bear a resemblance to Nirvana and the Foo Fighters, it's no secret that the members of this trio obviously know the ins and outs of their respective instruments