Heady head-bangers that flow together, from start-to-finish, on an infinite loop. The seven-piece Australian rock outfit is known for making concept albums, so it’s no surprise that the ambitious Nonagon Infinity adds a layer of structural symbolism to the mix. Fans will have a field day debating the meaning behind a never-ending LP: Is it a metaphor for constant touring? A nod to psychedelic rabbit holes? It’s hard to say for sure, but fun to find out. With melodic, surf-rock jams like “Big Fig Wasp” morphing into industrious, raucous numbers like “Gamma Knife”, the band has assembled an exhilarating musical obstacle course. Those with serious endurance can keep listening, again, and again, and again.