Thrice enters conceptual territory with The Alchemy Index, a four-part homage to the classical elements of fire, water, earth, and air. Turning to prog rock is a tricky move for any band to make, particularly one on the Vagrant roster, and Thrice tackles the project’s fire and water themes — both of which are given their own EP and packaged together to comprise Alchemy’s first double-disc set — with a cumbersome approach. The problem isn’t necessarily the music, since the “Fire” disc is very similar to Thrice’s previous work. Rather, the group simply handles these discs too literally. “Fire” is predictably incendiary, with giant riffs and gruff, throaty vocals laying the foundation for such self-evident song titles as “Firebreather,” “The Arsonist,” and “Backdraft.” The “Water” disc follows a similarly strict pattern, as ambient electronics and seafaring metaphors mix together for “Night Diving,” “Digital Sea,” and four other slow jams. These watery songs are actually quite good; their vaguely Coldplay-esque sound is a far cry from Thrice’s hardcore past, but it’s still refreshing to see the band stretch its boundaries with neo-Beach Boys harmonies, programmed percussion, and Dustin Kensrue’s best Chris Martin impression. What The Alchemy Index lacks, then, is integration. There’s no crossover between the two elements/styles, and the whole effort seems stilted as a result. Examining classical elements is a novel concept, but spreading that concept throughout four EPs, two double-disc sets, and two record releases does little more than dilute an otherwise strong set of songs. – Andrew Leahey