Heritage, Opeth's tenth studio offering, finds the Swedish band abandoning death metal: no growled vocals, no blistering fast power riffs, no blastbeats.

Mixed by Steven Wilson (Porcupine Tree, King Crimson) and engineered by Janne Hansson, Heritage is easily Opeth's most musically adventurous -- and indulgent -- recording.

Written primarily by vocalist/guitarist Mikael Åkerfeldt, these ten songs are drenched in instrumental interludes, knotty key and chord changes, shifting time signatures, clean vocals, and a keyboard-heavy instrumentation that includes Mellotrons, Rhodes pianos, and Hammond organs -- ironic since keyboardist Per Wiberg left the band after Heritage was completed.

Opening with the title track, a haunting solo piano instrumental, it careens into the explosive "The Devil's Orchard," with spectacular, arpeggiatic guitar work by Fredrik Åkesson and matching drums by Martin Axenrot.

With a huge, swirling B-3 in the backdrop, it melds progressive metal to prog rock, with Åkerfeldt's clear, clean singing.

"I Feel the Dark" marries Åkerfeldt's classical guitar to piano, flute, a droning Martin Mendez bassline, and double-timed, quietly tense drum kit work.

"Slither" sounds like Motörhead meeting early-'70s Deep Purple.

"Nepenthe" begins as a ballad but shifts toward jazz-rock in the instrumental break before finding its way back to a middle ground with sparse instrumentation and taut dynamics.

"Haxprogress" draws real inspiration from early King Crimson; Mellotrons and nylon-string guitars give way to Åkerfeldt's crooning, thundering basslines, and syncopated drums.

At eight-and-a-half minutes, "Famine" is the album's most abstract cut, with guest Alex Acuña adding Latin percussion to the mix, creating spaciousness in a long intro before giving way to colliding prog rock at the seam where King Crimson's "Larks Tongues in Aspic, Pt.

2" meets Jethro Tull's "Thick as a Brick." "The Lines in My Hand" is the set's most aggressive cut, with a deeply satisfying guitar crunch.

"Folklore," with its myriad instrumental and vocal parts, complex melody, and breakbeats, comes off as an eight-minute suite before closing with another jazz- and folk-inflected instrumental entitled "Marrow of the Earth." Love it or hate it, Heritage, for its many excesses and sometimes blurry focus, is a brave album.

It opens the door for Opeth to pursue many new directions and reinvent themselves as a band.