Songs that change completely (and stay that way) somewhere in the song.

Of course TV Tropes has a name for this.

Here’s some more that I don’t think have been mentioned there, or in this thread:

“Who’s To Blame” by Sacred Reich

“Paranoid Android” by Radiohead (video NSFW, as well as incredibly strange)

“B.Y.O.B.” by System of a Down

“San Jacinto” by Peter Gabriel (although not until 5:22)
“Little Black Submarines” by Black Keys

Two that come to mind:
Jethro Tull - Locomotive Breath
Moody Blues - This Word is Om

How about the Kinks’ “Shangri-La,” or their “The First Time We Fall In Love.”

I guess you could also look for songs that identify themselves as a suite (like Styx’s “Suite Madame Blue,” Crosby Stills & Nash’s “Suite: Judy Blue Eyes,” or the Swirling Eddies’ “Ed Takes a Vacation (A Suite)”).

Oh and also “Carry On” by CSNY as well.

“Fairytale of New York” by the Pogues. The opening melody, which is slower than the rest of the song, does return at the end, but in the same faster speed as the rest of the song.

Oh, CS&N’s “Daylight Again”.

http://https://www.youtube.com/watch?v=1cjR5QHFpEo

Sorry, I’ve never been smart enough to figure out how to label links. But this one directs you to the first song I thought of with this format. Mother of Pearl Roxy Music.
Starts off with a fast rocking’ beat and merges into a mellow ongoing groove.

“Birdman” and “Suite in C” by Mcdonald and Giles.

Hey Jude by the Beatles
We Are the Champions by Queen
Does Sgt. Pepper’s Lonely Hearts Club Band/ A Little Help from my Friends count as one song?

“You keep using this word. I don’t think it means what you think it means.”

I’d say no, and neither do “We Will Rock You”/“We Are the Champions.” What they are is songs that are almost always played together, which is the subject of other threads: Songs commonly played together; We Will Rock You / We Are the Champions - same song?; Songs Commonly Played back-to-back; Songs by one artist that are always played together, rock and otherwise

Unfortunately I can’t link to it from this device, but “Reynard the Fox” by Julian Cope fits the bill nicely (it’s on YouTube).

On a phone so I can’t link, but Foo Fighters have one on their new album called"Something from Nothing." It’s a bit unusual for them but I like it.

I thought of “Supper’s Ready,” which definitely goes through several different subsongs in different meters and leaves most of them behind, but I’m not sure it counts, because it kind of comes back to the original tune at the end. It’s sort of a concept album in one roughly continuous track.

Just heard one that possibly qualifies. It starts as a standard soul song of the '70s, then breaks into one of the best funk grooves of that decade, Diana Ross’s Love Hangover, with the break occurring @ 1:10 into the song.

Cashman and West’s American City Suite has three parts so completely different that the end piece, A Friend Is Dying, was even played seperately as a stand-alone.

I have “The Yes Album” in my car’s CD player right now! Don’t forget “I’ve Seen All Good People/Your Move” and “Perpetual Change.” My favorite “switch” is the one in “Perpetual Change” at 7:22.

Roy Clark’s Thank God and Greyhound You’re Gone

There’s also the Guess Who’s “No Sugar Tonight/New Mother Nature”.

The story behind that is that they had two songs they really liked, and neither was quite long enough to release as a single, even in that era, and since they were in the same key signature, they decided to fuse them.

American City Suite by Cashman and West, maybe? Although anything called a “suite” probably is expected to do this kind of thing.