There's nothing written in stone about golden-age classic rockers having to continue down the same path as they enter their later years. It works for some: Mick Jagger, Paul McCartney and Neil Young have done well without steering too much off course throughout the decades. But others no longer fight the urge to bust the same moves they did 50 years earlier, when they had full heads of hair and all of their original body parts.

Robert Plant has pretty much made a second career rewriting and rewiring his past. Since the turn of the century the former Led Zeppelin singer has packed away his hard-rock tendencies and dived deeper into Americana, blues and world music, peaking with 2007's collaboration album with bluegrass star Alison Krauss, Raising Sand. His '10s output – including 2010's Band of Joy, 2014's Lullaby ... and the Ceaseless Roar and 2017's Carry Fire – are among the most satisfying records ever released by golden-age rockers during their golden years.

Plant and Krauss' long-awaited sequel, Raise the Roof, picks up where Raising Sand left off 14 years earlier and once again finds the middle ground between the Brit and the American's off-course tastes. The pair – there's a 23-year age difference between them – have made it clear their backgrounds and record collections rarely intersect; it's their mutual respect and musical openness that have made their collaborations a perfect blending of two seemingly disparate worlds.

Like Raising Sand, Raise the Roof is filled with folk, country and blues covers. "High and Lonesome," the sole original, was penned by Plant and producer T Bone Burnett and is a moody highlight. But that song's inspiration comes from the same atmospheric place as the album's other 11 tracks. Whether it's 21st-century alt-country (Calexico's "Quattro [World Drifts In]"), rock 'n' roll pioneers (the Everly Brothers' "The Price of Love"), Scottish folk heroes (Bert Jansch's "It Don't Bother Me") or later-period obscurities from '70s singer-songwriters ("Somebody Was Watching Over Me" from Maria Muldaur's 1996 album Fanning the Flames), Plant and Krauss bend each track to their worldview here.

The lines between the singers and their source material are blurred to the point where most of the songs effectively become Plant and Krauss numbers. Look no further than the opening "Quattro (World Drifts In)," in which their voices – Plant's deep growl, Krauss' sugarcoated higher register – meet somewhere in the middle, or how Plant reworks Anne Briggs' gentle folk song "Go Your Way" into one of Raise the Roof's toughest tracks. Burnett's dry and occasionally brittle production complements the tasteful arrangements – filled with soft, rolling drums, echoing guitars and open-aired empty spaces that are almost another instrument here – to the point where you really can't imagine these songs sounding any other way. 

All of these things led to the award-hogging Raising Sand to become a new standard in the decade and a half since its release. Raise the Roof matches it every step of the way.

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