Is it possible that a Led Zeppelin album could be underrated? If so, I nominate 1970’s Led Zeppelin III for the award, sandwiched as it is between the epic high-water mark of IV with its eponymous beauties “Black Dog” “When the Levee Breaks,” “Going to California” and the eternally enduring boat ride down the Styx that is “Stairway to Heaven;” and the raucous raw-dog one-two blues punch of, well, I & II.

Led Zeppelin III seems perpetually overlooked even though the opener, “Immigrant Song” and the jangly blues instrumental “Bron-Y-Aur Stomp” are respected classics in their canon. Perhaps there is a reason for this. While I & II are arguably of a seamless piece (they were released within months of each other in the same year), they are also fairly straightforward. Heavy doses of loud fudgy rock with dirty sex-laced blues, each song an exploding cannonball of energy and attitude.

No one squeezes anybody’s lemons on III. It is an album of subtle, elusive meanings that despite all the glories of its tight rock and roll sound is as delicate, experimental and perfected as an engraved silver ring or a beautiful gown made of lace (which will inevitably be slipped off before Side B has run out).

III is generally regarded as their first “folk album,” and while it does seem to take its cues from II’s classic “Ramble On,” with its eerie references to Lord of the Rings, the broad term “folk” is both insufficient and misleading.

The British Folk movement of the late 1960s was a galaxy removed from its U.S. counterpart: Peter, Paul and Mary crooning a capella harmonies about hammers; doleful losers in berets and Hush Puppies preaching at hip coffeehouses; neo-hippie farmers extolling the virtues of dirt, love and sunshine…

British folk dug back to the roots of English music itself—the old popular tunes and ballads of the rural countryside passed down through the centuries. In this respect it had more in common with the Appalachian fiddle tunes of American country and bluegrass. The themes of the songs carried the last vestige of the earliest agrarian rites and customs—a dark, bloody, mystical pre-Christian past disguised in sorrowful murder ballads and symbol-rich fairy tales.

But most importantly, the songs of the British folk music weren’t airy, insipid harmonies plucked on lutes and zithers, but hard-charging rhythmic affairs that brooded and ambushed, reeled, jigged and ran headlong through dark, dangerous thorny thickets. They were full of a heavy air of doom and fear, their heroes and villains mere playthings of the natural and supernatural worlds.

Fairport Convention took the movement to its zenith with 1969’s Liege & Lief, an album that greatly influenced Led Zeppelin III, released less than one year later. Compare Zep’s opening rocker “Immigrant Song” in rhythm and pace to Fairport’s “Tam Lin.” Both songs are marked by punching rhythmic guitar riffs connected by disembodied mystical howls to tell tales from England’s pagan past. The connection is no mere coincidence, as Robert Plant brought Fairport lead siren Sandy Denny to duet on IV’s Wagnerian “Battle of Evermore.”

In direct imitation of Liege & Lief, of whose eight songs only two were band originals, Zeppelin reaches back primarily not into American blues history as on I & II, but their own English folk music, reclaiming “Gallows Pole” and “Bron-Y-Aur Stomp” from obscurity and reworking them into rock jewels.

Craftsmanship in many forms was a hallmark of Europe’s pre-Christian pagan cultures. Grave findings from Norway to Northumbria reveal exquisite embroidery, hand-carved combs and clasps, runic inscriptions in stone and wood, spectacular gold, silver and copper metalwork: rings, cauldrons, bowls and helmets worked with flawless engraving; minted coins and elaborately finished weapons and shields-- all of it wrought on heavy, organic elements used to slaughter, reconcile and subdue lying beside skeletons of people whose bones were broken by battle, torture or ritual sacrifice.

It is this potent blend of inspired artistry, fine workmanship and savage power that defines Led Zeppelin III, and renders it a true and worthy document of the British folk tradition.