Foreigner joined a short and distinguished list of superstar bands whose fourth albums became their signature albums (see also Led Zeppelin and Toto) when they released 4 on July 2, 1981.

When the time came for work to begin on 4, guitarist Mick Jones and Atlantic secured the services of producer "Mutt" Lange, who was fresh off his unprecedented success behind AC/DC's Back in Black, and had a reputation for being as hands-off as producers came.

"[Mutt] wanted me to play every single idea I had on cassette. He said that it didn’t matter if I was embarrassed, he just wanted to hear everything," Jones later told to UCR's Matt Wardlaw. "So I played him everything, and out of that he picked two or three gems. I had the riff starting out 'Urgent,' and he picked that out and I said, 'That’s like an experimental instrumental thing that I’m working on.' And he said, 'No, it isn’t anymore. Let’s take that one, because that’s got a lot of potential.'"

A new, opinionated producer wasn't the only novelty at hand when they entered New York's Electric Lady Studios. 4 also showcased Foreigner's reduction to a quartet of Jones, singer Lou Gramm, bassist Rick Wills and drummer Dennis Elliott, following the departure of Ian McDonald (rhythm guitar and keyboards) and Al Greenwood (keyboards), whose parts would be handled by synth-pop pioneer Thomas Dolby.

Resulting melodic hard rockers like "Night Life," "Break it Up" and "Don't Let Go" combined those generous synths with the muscle of AC/DC, "Luanne" infused them with a '50s rock innocence, and the progressively moody triple threat of "I'm Gonna Win," "Woman in Black" and "Girl on the Moon" battled for light and darkness across side two.

At times, it seemed that Lange's recent producing experience – both with AC/DC's bruising sound and New Wave of British Heavy Metal stars Def Leppard whose High 'n' Dry LP he had only just finishe – didn't jibe with Foreigner frontman Lou Gramm's view of things.

Watch Foreigner Perform 'Urgent'

"Mutt was a nice guy, very knowledgeable and knew how to get the best out of you, but a lot of things he did at the time were derivative to AC/DC," Gramm told Guitar World in 2013. "He'd often try to get me to sing like Brian Johnson. Now I could tear it up and sing tough songs, but I certainly didn’t sound like Brian Johnson, so I pushed back."

Ultimately, there would be no evidence of AC/DC in the alien synth introduction and dynamic stop-starts that dominated 4's anthemic "Jukebox Hero," let alone its monster ballad "Waiting for a Girl Like You," which was in fact tailor-made for the MOR sounds dominating America's radio dial. Clearly, Foreigner and their strong-minded producer had found a way to see their disagreements to a compromise.

Jones told Wardlaw that the relationship "almost ended a few weeks into it, just through arguments and a whole bunch of stuff going on, but by the time we finished we were the best of friends — and, thankfully, we still respected each other very much. I know I respect Mutt for what he’s done. He definitely gave us a tough time, but he got it out of us."

Foreigner's mission was accomplished when the album's first single "Urgent" (famed for Junior Walker's electrifying saxophone break) climbed to No. 4 on the Billboard Hot 100, soon bettered by "Waiting for a Girl Like You" at No. 2. Both songs hit No. 1 on the rock chart, and the latter earned platinum-sales status. Third single "Jukebox Hero" then rose to No. 26, becoming one of Foreigner's most popular tracks.

In the end, 4 topped the album chart for an amazing 10 non-consecutive weeks, ultimately selling an estimated seven million copies worldwide. The LP was perhaps Foreigner's very finest hour, and one whose best-loved songs remained fixtures of the band's concerts for decades.

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