I know I bring them up a lot, but Supertramp's another great example of this.
Their first two albums, Supertramp and Indelibly Stamped, are best described as easy listening and sound more like late 60's rock than the progressive stuff they got known for later. There are some songs on these albums that sound NOTHING like their more popular stuff, especially songs like Potter which don't feature Hodsgon or Davies singing the lyrics. Honestly that guy sounds like a wannabe Mick Jagger.
Crime of the Century, usually considered their best album, is a progressive rock/art/concept album, and in my opinion, one of the most underrated classics in the genre. It tells an interesting and poetic narrative which can be interpreted in a variety of ways. I usually interpret it as a single person's descent towards madness due to social pressures. If you're a Pink Floyd fan, you'll love this album, although there is a bit of weirdness here too (such as Dreamer).
Crisis? What Crisis? is completely different. In my opinion it's the most coheisive of their albums. I would consider it mainly soft rock.
Even in the Quietest Moments… lives up to its title. It's a quiet, relaxing album that shares little in common with its predecessor (outside of possibly the song "The Meaning"). It's an art album but this feels more like Davies's jazz influences have spread more here as opposed to Hodgson's psychedelic rock influences found scattered through Crime. Outside of "Give a Little Bit" and "Babaji" most of the songs are slow paced and based on narrative rather than standard rock faire.
Breakfast in America is first and foremost a pop rock album, sounding almost nothing like Crime of the Century 5 years prior. Still a great album though. You can still see the progressive side of the band coming through on a few songs, especially The Logical Song.
I'm not a huge fan of Final Last Words, I think it's best described as a pop rock album but it doesn't really have the integrity that BiA has in general.
After Hodsgon left in 1983, Rick and the boys put out Brother Where You Bound, which, in my opinion, is the last great Supertramp album. Here they return to a fiery political narrative through heavily progressive rock sounds. It's only 6 songs but it's very clearly art/progrock.
Free as a Bird is a sell out album. Haven't listened to Some Things Never Change.
Slow Motion, their last album and a somewhat obscure album, is pretty jazzy, although it does return to some of the roots of the band. I kind of feel this is what Supertramp would sound like if Roger never got involved.
All in all the band bounced quite a bit around with their production. While they did make a temporary return to progrock, they basically bounced between rock genres every album or so. Listening to "Aries" on Indelibily Stamped is so weird in comparison to "The Logical Song" on BiA or "Hide in your Shell" on Crime.
Also, I can't really give any samples because this band is one of those bands where you do have to listen to the whole album in a row and because of copyright bullshit I can't really share them from youtube.
Interestingly, Roger really doesn't sound that much different from his stuff in BiA in his solo career outside of the mess that's Hai Hai. Both Open the Door and Eye of the Storm basically sound like Supertramp if Roger just wrote a whole album and didn't use keyboards.