Relayer is Yes’ metal album. OK, that’s an exaggeration. But it is their hardest, most aggressive, wildest, noisiest release. Keyboardist Rick Wakeman left the group after the tour in support of 1973’s bloat-tastic double disc, Tales From Topographic Oceans, and they replaced him with Patrick Moraz, a relative unknown from Switzerland, of all places. Ducking into the studio, they emerged with a dark mirror image of 1972’s Close To The Edge — one song on one side, two on the other, all of them full of time shifts, multi-part vocal harmonies, intricate guitar-keyboard interplay, and churning rhythm work from Chris Squire and Alan White (as opposed to Bill Bruford, who played on Edge).

The album’s first half, the nearly 22-minute “Gates Of Delirium,” is easily and by far the most insane track recorded in Yes’ classic era. Built around an angular, twang-metal guitar riff from Steve Howe with Moraz zapping and zinging around behind him, it travels through a series of related but discernible movements. Atop it all, Anderson’s vocal melodies are less mantralike than they were on Tales From Topographic Oceans, and more like a traditional song — not necessarily the same one the band’s playing, though. He’s off in his own world, and they’re in theirs, and occasionally the mathematical formulas being diagrammed by the rhythm section bring everybody into line. The long instrumental section in the middle of the piece is breathtaking and bizarre, verging on Mars Volta levels of intensity at times, even before taking into account the explosive junk-percussion break. That’s right, Yes goes full-on Einstürzende Neubauten on this one, clanging and clattering and bashing away as Howe and Moraz solo in manic oblivion. Seriously, “Gates Of Delirium” lives up to its title.

The two tracks on the second side of Relayer kind of pull back from the cliff’s edge that “Gates Of Delirium” ran the band up to. “Sound Chaser” features Howe getting all crazy-fingers again, but in a slicker, Euro-rock way that prefigures their next album, Going For The One; he’s almost boogieing, and Anderson’s vocals almost recall “Roundabout” in their punchy directness. Album closer “To Be Over,” meanwhile, is a gentle ballad with an atmosphere like a rainstorm in a greenhouse; Howe’s slide guitar playing sounds like Hawaiian legend Sol Hoopii gone sci-fi. Relayer is as weird as Yes ever got, and is unique in their catalog for exactly that reason: You can’t pull a trick as dense, baffling, and awesome as this more than once.