A definitive set of criteria to determine what makes a concept album is, by the very nature of what concept albums are, difficult for even the most musically inclined to pin down. Considering they can be as easily panned as they can be praised, it takes a conscious decision for a band to make that kind of creative leap of faith and hope their fans will jump with them. Unless, of course, you’re a member of Thrice, and concept albums just unwittingly happen to you.

The Irvine post-hardcore-prog-rockers – made up of bassist Eddie Breckenridge, drummer Riley Breckenridge, vocalist Dustin Kensrue and guitarist Teppei Teranishi – didn’t set out to have their follow up to 2005’s Vheissu be on any large conceptual scale. Neverthelesss, the resulting product took form as a four-part aural odyssey that functioned as the culmination of the band’s previous five years of songwriting while setting the stage for all the new tricks the band had, and still have, in store.

Starting with last year’s The Alchemy Index, Vols. 1 & 2: Fire and Water and completing with this year’s Vols. 3 & 4: Air and Earth, the band used the four classical Greek elements as the template on which to paint a risky masterpiece.

“It was an idea Dustin came up with, and when he shared it with us, we didn’t really have an idea of how we were going to theme each record or what sonic characteristics each was going to have,” says Riley, the elder of the two Breckenridge brothers. “A lot of people were like, ‘Oh, they’re making a concept album, that’s so pretentious,’ but we’re just trying to have fun, it’s not about trying to look cool.”

No strangers to criticism while pushing the musical envelope, however, the band remained undeterred.

“We tried to not waste too much time with getting the perfect take, it was more about capturing the moment and a certain vibe for each EP. It was an interesting challenge and a little overwhelming at first. We had to learn to trust each other and trust our abilities.”

Luckily, Breckenridge and his band mates haven’t taken much backlash from longtime fans.

“For the most part, the reception has been positive. There are a few people who want us to return to making the records we were making five years ago, but that’s never going to happen,” he says. “If you spend too much time thinking about what other people are going to think about you’re doing, you lose the purity of whatever you were working on. You just have to trust your gut and make sure that you’re happy with the end product. Whatever happens after that is up to chance.”

While many artists would be quick to rest on their laurels for an album well done, Breckenridge is ever the humble musician and is quick to deflect praise that often crosses into idolatry from diehard fans.

“I’m really hard on myself and I don’t take compliments very well, so it’s always tough for me,” he says. “While I appreciate it, it’s hard to grasp and it has everything to do with me not being comfortable with where I am as a musician and I think we as a band have a lot more to do and we don’t want to get complacent.”

Asked which element he found most representative of himself, Breckenridge says he has an equal affinity for both fire and water, a metaphor which, in turn, has quite a bit of symmetry to his band’s ability to aggressively redefine and rebirth themselves without being volatile or alienating older fans. And though past albums have been stylistically and thematically varied, one thing that the members of Thrice have always made clear in their music is that artistry, integrity and the importance of doing something for a greater purpose are neither lost methods of old nor mutually exclusive to being in the modern music industry.

Arguably the biggest and most difficult overarching theme an artist can convey throughout their oeuvre, perhaps Breckenridge and his band mates are finally just getting credit for something they’ve been doing all along.

The Alchemy Index, Vols. 3 & 4: Air and Earth is currently available. Thrice will perform May 27-28 at House of Blues Anaheim. For more information, visit www.thrice.net.