Before Def Leppard sold 25 million copies of Hysteria, even before Pyromania sold 10 million, they sold next to nothing of an album many devoted fans consider their very best: High 'n' Dry.

It didn't earn platinum certification until more than a decade later, but High 'n' Dry is where Def Leppard came of age and established their signature sound, under the helpful tutelage of super producer Robert John "Mutt" Lange. And the rest was history.

It all starts back in 1979, when an inexperienced but ambitious Def Leppard became one of the very first New Wave of British Heavy Metal bands (even though they never felt a particularly strong kinship to the movement) to release some a record – the immensely collectible Def Leppard EP. Then, little more than a year later, in March 1980, the young Sheffield, England-based quintet of singer Joe Elliott, guitarists Steve Clark and Pete Willis, bassist Rick Savage and drummer Rick Allen unleashed its first full-length album, On Through the Night.

The following year, Def Leppard toured across the U.K. in support of major acts like AC/DC, Judas Priest and Sammy Hagar, but their album's initially impressive No. 15 chart peak had been eclipsed within a month by Iron Maiden's eponymous debut (which went to No. 4), leaving Def Leppard playing second fiddle to the London-based rock press' hometown boys.

Nevertheless, salvation was at hand with the intervention of Def Leppard's powerful manager, Peter Mensch, who also handled AC/DC, and was able to convince Highway to Hell and Back in Black producer Lange to sign on for his rising clients' next album sessions, due to begin in March 1981. In Lange, Def Leppard encountered an exacting taskmaster willing to do whatever it took to elevate their game and get them to the major leagues, and even though his perfectionism nearly broke the band's spirit, along the way, they eventually emerged triumphant.

Watch Def Leppard Perform 'Let It Go'

The impeccably crafted hard rock of High 'n' Dry achieved a perfect balance between brawn and beauty, with songs like "Let it Go," "High 'n' Dry' (Saturday Night)" and "You Got me Runnin'" meshing riffs and melodies, rhythm and lead guitars with a serpentine grace the likes of which heavy music had rarely witnessed. In a word, these songs had class – and that meant bridging the demographic gap to reach a female audience that, in 1981, remained largely out of reach for heavy metal acts.

With Lange at the helm, Def Leppard would soon make a career out of redefining and breaking down boundaries, but for High 'n' Dry, what lay ahead was condensed into the album's requisite power ballad, "Bringing on the Heartbreak" (a hit, but one that came several years later in a slightly remixed form), and, to a lesser degree, in the dark romance of "Lady Strange" and "Mirror, Mirror (Look Into My Eyes)."

But make no mistake: based on the sonic definitions of the early '80s, Def Leppard were still very much a metal band, and fierce, head-banging anthems like "Another Hit and Run," "On Through the Night," "No No No" and the instrumental "Switch 625" showed enough spirit keep the band competing with metal peers like Iron Maiden, Saxon and Diamond Head had they chosen to.

But they didn't, and Def Leppard still had to fight to see their vision through, because, High 'n' Dry wasn't a hit upon its release. While the album reached a respectable No. 51 in the U.S., in their U.K. homeland, sales fell short of the debut, prompting The N.W.O.B.H.M. Encyclopedia to claim a certain amount of prejudice stoked by the British press – specifically because Def Leppard wanted to conquer America.

It was only a matter of time for Def Leppard and Lange: first with 1983's breakthrough Pyromania then 1987's planet-dominating Hysteria and finally a long list of multi-platinum albums afterward. Each experimented with new technology or songwriting directions, but the blueprint for their perseverance, imagination and eventual success goes back to High 'n' Dry.

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