Usually this happens when an artist or a band is after commercial success. So they might would change their sound drastically just for the sake of it.
(Songs in alphabetical order)
1) Abracadabra by Steve Miller Band (1982)
Abracadabra was the most commercially successful song by Steve Miller Band, but compared with band’s average dark Bluesish sound, this one sounded more Poppish. The only song of theirs which is closer to the sound of Abracadabra, would be the also upbeat Poppish song, Serenade.
2) Addicted To Love by Robert Palmer (1985)
Robert Palmer changed his style many times, but I’d say his average style was Blue-Eyed Soul. He was also involved with Synth-Pop in the early 80s. Addicted To Love on the other hand was an AOR song, and probably the only AOR song coming from him.
3) Dancing In The Dark by Bruce Springsteen (1984)
Bruce had many hit songs, but I think Dancing In The Dark was his most successful one from a commercial point of view. But it was way different than his typical style (Heartland Rock), leaning towards a more Synth-Pop direction, which is unusual for Bruce.
4) Golden Brown by The Stranglers (1981)
Sure, The Stranglers mellowed their sound since the 80s started, but even by La Folie (the album from where the single Golden Brown was lifted) standards, Golden Brown was way different featuring a Baroque Pop style, different from the quirky New Wave sound of the album.
5) I Don’t Like Mondays by The Boomtown Rats (1979)
Their most famous hit was a piano-based Pop ballad, featuring no guitar at all. I’d say here they weren’t themselves, but a different band. Their most boring song in my opinion.
6) I Was Made For Loving You by KISS (1979)
Fun fact: When I was like 14-15, I knew this tune, without knowing the song’s title or who was singing it. When I came across the title and noticed the band was called KISS, I assumed it was some Disco band (the band’s name is kinda misleading too)
So yeah, it was a massive surprise when I found out they were a Hard Rock band.
7) Live Is Life by Opus (1985)
A party song that it was a big-hit in the mid-80s around Europe, and it’s considered an all-time classic in many countries. But the rest of their discography is more obscure and not so accessible as Live Is Life.
8. Macarena by Los Del Rio (1995)
Los Del Rio existed for three decades, before they make it big with Macarena, which became a phenomenon by the mid 90s along with the notorious Macarena Dance. The original 1993 version from their A mi me gusta album, was more related to their sound, and not the 1995 version with the female vocals which was the version that made them international superstars.
9) Nothing Else Matters by Metallica (1991)
Many consider Metallica being sell outs after the Black Album, when they made their sound more accessible to the casual listener abandoning their Thrash Metal roots. Still the Black Album wasn’t soft by average standards, yet it was soft compared with what Metallica did before. Nothing Else Matters was soft even for Black Album’s standards, but it became their biggest hit.
10) Owner Of A Lonely Heart by Yes (1983)
Yes were already famous for their Progressive Rock material, but they were too complex for casual listeners. Their album 90125 is considered their Poppiest album, but still it’s not as accessible as the lead single, Owner Of A Lonely Heart which was more or less their only song with a Pop, radio-friendly sound.
11) Relax by Frankie Goes To Hollywood (1983)
Their sound on their first album Welcome To The Pleasuredome wasn’t definitive at all actually. It was a weird blend of various genres altogether and some interludes thrown in. Their most recognizable tune, Relax, was a Synth-Pop song. The only other song closer to Relax’s sound would be Two Tribes which was also a big hit for the band. Anything else was way different, so we could say Frankie Goes To Hollywood don’t belong in the Synth-Pop realm.
12) Sledgehammer by Peter Gabriel (1986)
It’s true that Peter Gabriel was involved with many styles. And also it’s true that his album So was his most radio-friendly album. But Sledgehammer sounds like it’s not him, because it sounds too "Black" for his standards.
13) Take My Breath Away by Berlin (1986)
Sure this song gave them international success, but it was way different from what they did before. Take My Breath Away was a Pop Ballad, famous from the movie Top Gun, but not related to the sound of their New Wave stuff they were known before.
14) Tempted by Squeeze (1981)
Sure the album East Side Story had a diversity of styles, but generally other songs from the album, fitted a little bit more to what Squeeze have done before. Tempted on the other hand was more like a Soft Rock song, closer to the likes of artists like Billy Joel or Christopher Cross.
15) True by Spandau Ballet (1983)
By the time True (the album) was released, Spandau Ballet changed their sound again, making it more commercial and radio-friendly. Maybe the song I’ll Fly For You is slightly closer to the sound of True (the song this time), but generally Spandau Ballet had more upbeat songs, unlike the Soul Ballad True, which would make you believe it was written by some Black artist.