Ever noticed this famous Zeppelin song is reminiscent of a famous earlier Doobie Brothers Song?
Trampled Underfoot from Physical Graffiti (from 1975 though it's known to have a lot of songs written for past albums on it, like Houses of the Holy)
Slow Train Running (1973)
It's not just the constant repetition of the word love ... the relation has a deeper music theory component.
And it's not in the same key, not quite that simple ... so what music nerd can explain why they sound similar?
= new reply since forum marked as read
But I’m not sure how to describe it.
Kind of like the same guitar riff played throughout both songs in the background? Is that the correct term?
Pretty good observation - I’ve heard both songs numerous times but never put them together like that.
Full disclosure, Mandy's the one who made the connection as we were listening to it just now. She has a lot more theory knowledge than I do, and knows her classic rock
The vocal part from Plant is what you should sing to someone if you said “what’s that doobie’s song, the one that goes…”
Theoretically, iirc, long train runnin’ is a chord progression that the top notes are a half step change. I think it’s a d-minor7 (a top) to a g-minor7 (Bb top). That might be the progression under plant’s vocals too, albeit with a different rhythm pattern.
That’s reaching back 35 years but I think it’s why you’re hearing the two the same.
Besides certain lyrics and cadences in the vocals, Long Train is B flat major and Trampled is G minor ... which are two very closely-related but not identical key signatures (varying only on where you start the progression).
So says my lady anyway 
A Bb maj9 and a Gm sus9 can be the same 4 notes (C D F A). Same with a Bb6 vs a Gm7 (D F G Bb). Bass player drives the major minor feeling depending on his patterns and where they resolve.
Never thought much about what key the song is but yeah, I can hear Johnston and Page playing pretty much the same chords/position with the songs being in those two keys.
Cool.
Kashmir
Tell me that’s simplistic, go ahead. I dare ya. I double dare ya.
3 chords. Com’on man. 
But…I ain’t gonna stand up for Townsend but ya didn’t have to take a swing at Richards or Gilmore to make the point. Lol.
I think you're hearing things!
There not just in a different key, Long Train is accented on the 1 & 4, while Trampled is on the 2 & 4.
As to the melodic similarity, there are only 6 notes that define a melody. At the end of every phrase on the Doobie's song, he goes up. Plant doesn't.
Given there's only the 6 notes, it's easy to find melodic similarities then separate by details like timing & phrasing.
I hear a LOT of differences in phrasing.
There is far more different than the same.
