Songs that evolved into other songs

There's a track on Monster Movie by Can that has a central riff that's revisited on a track on Tago Mago. Is it Outside My Door to Mushroomhead?
Might show how the 2 different singers influenced the development of an improvisation?

what's that Wilco song that uses Rocket from the Tombs lyrics

Is it cheating to say that many old blues songs became Led Zeppelin songs?

I dunno about "many"

Zep re-appropriated a lot of stuff though - just as much left-field folk as blues imho

John Renbourn, Bert Jansch, Spirit, Joan Baez

Andy Partridge came up with XTC's 'Books Are Burning' after messing around with the chords from The Beach Boys' 'I Get Around'. 'Stupidly Happy' was written after he jammed Rolling Stones riffs over a drum machine.

There's a difference between being influenced/ripping off another song and releasing a new version of a song that had originally appeared somewhere as a "first draft".

For example,

https://www.youtube.com/watch?v=HvCUJgnVg3o

https://www.youtube.com/watch?v=6hzrDeceEKc

https://www.youtube.com/watch?v=UeCcuH-EsuM

(Of course, with Oasis, it was usually the other way around, but not in this case)

Led Zeppelin infamously ripped off loads of blues and folk musicians, but here they ripped off themselves in their previous incarnation as the Jimmy Page-era Yardbirds (and also ripped off Keith Relf, who was uncredited for Zep's "Tangerine" even though it retained a full verse of lyrics he wrote for "Knowing That I'm Losing You" from the Yardbirds' last studio recording session from early 1968). Same basic verses, but complete different melody and lyrics on the chorus. Check out the Mellotron!

https://www.youtube.com/watch?v=fPh1r32TCMY

songs that sound like other songs

that's pretty wild, Lee.

Another from The Who: "Naked Eye" partially evolved out of the "My Generation" jam on Live At Leeds (and their other early 1970 shows)

The instrumental break from "Havana Affair" became the riff for "Pinhead":

https://www.youtube.com/watch?v=M6UlXZxch-A

Steve Miller took a riff from his "My Dark Hour" and turned it into "Fly Like An Eagle":

https://www.youtube.com/watch?v=A61i8xsFkno

"I Wonder" by The Squires (featuring Neil Young) years later became part of Neil's "Don't Cry No Tears".

More Who:

While I wouldn't count demos -- that is, "Can you believe the demo for the song evolved into the song?" -- "Baba O'Riley" underwent several renovations before the Who even got hold of it.

First there was the 9 1/2 minute instrumental demo (which is fucking brilliant):
https://www.youtube.com/watch?v=v-layDeazY8&feature=results_video&playnext=1&list=PL6AD951471BEE5D25

Then the 7 1/2 minute demo with vocals:
https://www.youtube.com/watch?v=yh4wkMZXONc

Then there's a song called "Teenage Wasteland," using "Baba O'Riley"'s lyrics, but with a completely different melody and arrangement:
https://www.youtube.com/watch?v=tmbaWtQoLM0

D'oh, sorry, first link shoulda been this...sorry, didn't mean this to be so messy...
https://www.youtube.com/watch?v=v-layDeazY8&feature=results_video&playnext=1&list=PL6AD951471BEE5D25

OK, that still didn't work...search on YouTube for "Townshend Baba O'Riley Demo."

Was that the on-line equivalent of John Peel's "oops, wrong speed" there?

Something like that. Although, to the best of my knowledge, Peel never mixed vodka with RockStar energy drink.

Another Yardbirds/Led Zep example - the guitar solo (starting at 1:58) in the Yardbirds' "Think About It" was later recycled in its entirety for "Dazed and Confused":

https://www.youtube.com/watch?v=UseyCdGNfaY

Here are the Yardbirds performing "Dazed and Confused" in 1968:

https://www.youtube.com/watch?v=AYDhx_DgDxE

... and of course <i>that</i> song was merely a cover of this 1967 recording (the audio is awful on the Youtube post, with the classic descending bassline almost inaudible, but you can get the gist of it):

https://www.youtube.com/watch?v=pTsvs-pAGDc

and obv large swaths of hip-hop and rap samples or borrows from older songs

Stephen Stills took his Buffalo Springfield song "Questions" and made it the second half of the CSNY track "Carry On":

https://www.youtube.com/watch?v=zDjmmCvTH7o

Meanwhile Neil Young took his own (albeit unissued at the time) Springfield track "Down Down Down" and--after adding new lyrics--incorporated it into his CSNY jam suite "Country Girl":

https://www.youtube.com/watch?v=lgw9R2kzG3Q

The Monkees "Goin' Down" started out as the backing tracks for an intended cover of Mose Allison's "Parchman Farm," then they decided to write their own song on top of it instead.

Siouxsie & the Banshees "Peek-a-Boo" was built upon sections of the horns and drum tracks played backwards from their cover of John Cale's "Gun."

Wilco did Outtasite (Outtamind) and Outtamind (Outtasite) (I may have sic'd these titles slightly) on Being There.

"Revolution 9" developed out of the last eight minutes of the 20 minutes jam on "Revolution 1".

hey hey my my -> my my hey hey

Any reason why the song credits be different?

The title track on The Police's Reggatta de Blanc came from an extended jam they used to do live during the middle-eight of 'Can't Stand Losing You'.

I think they never stopped doing that middle bit, live.

One peel session had it as titled "the missing bit from the middle of "Can't Stand Losing You""

Ha!

Phish did this a bunch, mostly due to things evolving through live performance. The one I remember is the end section of "The Curtain With" evolving into "Rift".

Bob Pollard has reworked older songs countless times:

Wall and Windows became Hardcore UFOs
Crocker's Favorite Song > Class Clown Spots A Ufo
Tell Me > Tractor Rape Chain
Superwhore > The Who Vs. Porky Pig
Girl From The Sun > Do The Collapse
Reptilian Beauty Secrets > Idiot Princess
Sacred Space > Office of Hearts
Rocket Head > Teenage FBI
many more...