On July 2, 1981, 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.

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.

As Jones recalled to Ultimate Classic Rock's Matt Wardlaw, "[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. 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.'"

And a new, opinionated producer wasn't the only novelty at hand when they entered New York's Electric Lady Studios, for, as well as being Foreigner's fourth long-player, 4 also signified the band's reduction to a quartet (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.

In fact, at times it seemed that Lange's recent experience with AC/DC's bruising sound, as well as that of New Wave of British Heavy Metal stars Def Leppard (whose High 'n' Dry LP he had only just finished), didn't jibe with Foreigner frontman Lou Gramm's view of things.

Said Gramm to Guitar World in 2013: "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 ... 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."

There was certainly no evidence of AC/DC in the alien synth introduction and dynamic stop-starts dominating 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 AM dial. Clearly, the band and their strong-minded producer had found a way to see their disagreements to a compromise.

Once again when speaking to UCR's Wardlaw, Jones asserted 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.

Indeed, Foreigner's mission was accomplished when the album's first single "Urgent" (famed for Junior Walker's electrifying saxophone break) quickly 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, even as 4's third single, "Jukebox Hero," was rising to No. 26 (it would become 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. 4 ranks as perhaps Foreigner's very finest hour, and an album whose best-loved songs remain fixtures of the band's concerts to this day.

See Foreigner and Other Rockers in the Top 100 Albums of the '80s