Mastodon have shown a restless and inventive creative energy since they emerged in the early ‘00s, progressing from the sludgy, riff-driven metal of their debut to the jagged, jazz-inflected shards of 2011’s The Hunter. While the band's elaborate conceptual albums have been inspired by everything from Moby Dick to Rasputin, their sixth studio endeavor—Once More ‘Round the Sun—doesn’t revolve around a central narrative theme. Instead, the album’s focused and far-reaching songs stand on their own merits. The most powerful moments on Once More ‘Round the Sun are the most epic: like the chorus of "The Motherload” (sung by drummer Brann Dailor) and the soaring refrain of “High Road." The thrashing, turn-on-a-dime complexity of a tune like “Chimes at Midnight,” as well as the blistering guitar solo of “Halloween” are forceful reminders of Mastodon’s impressive ability to bridge metal’s heavy past with the genre’s inspiring future.