After releasing two gargantuan albums and trekking across the country on a nonstop touring schedule, Led Zeppelin needed an escape from 1969. To refresh the band members’ energy and conjure new musical spirits, the group relocated to a rustic 18th-century Welsh cottage named Bron-Yr-Aur in January 1970. The only song the band finished there was “That’s the Way”, which introduced a richly produced delicateness to Zeppelin’s palette, building from Led Zeppelin II’s muted “Thank You”. Jimmy Page’s acoustic tendencies had been mostly latent, save his refiguring of Scottish finger-picker Bert Jansch’s “Blackwaterside” as “Black Mountain Side” on the band’s debut album. But when Led Zeppelin III was released in 1970, the album featured a three-track run of acoustic tunes: “Tangerine”, “That’s The Way” and “Bron-Y-Aur Stomp”, a buoyant front-porch jam about Robert Plant’s dog. Anyone hearing the band for the first time could be forgiven for assuming they were listening to the latest Laurel Canyon folk-rock strivers. Strummy acoustic shift notwithstanding, this was still Led Zeppelin. By now the band’s reputation as marauding metal buccaneers was preceding them, and Led Zeppelin III’s darker parts demonstrate how the band members’ rustic reboot invested their hardest music with an earthy historicism. For a lesser group, opening your album by strapping on a horned helmet to dramatise the Viking raids on the British Isles would melt into cartoonish Dark Ages role-play. But this is Zeppelin at peak power, and between Page’s thunderous riffage and Plant’s Nordic wail, “Immigrant Song” is a heavy-metal war cry that hits with the force of an axe to the skull. While nothing else rocks nearly as hard on Led Zeppelin III, a tangible dread floats through the album, most notably on “Gallows Pole”, a frenzied folk-metal plea from a condemned man that the band culled from a Smithsonian Folkways compilation. Then there’s “Since I’ve Been Loving You”, the band’s finest original blues tune, and the sweltering “Friends”, which wafts out of the speaker on the thick, pungent aroma of John Paul Jones’ Moog drone. Led Zeppelin’s first two albums were made quickly; Led Zeppelin III is the first time the band let their music simmer, and the music’s tone and scope expanded as well.