The Layla riff is actually the riff from Albert King's "As The Years Go Passing By" so... Duane Allman is great I agree but I think you're giving him too much credit.
Well it are Clapton his words. I listened to the Albert King song and find it to be honest a far stretch that he borrowed it that way.
"When we had some songs we went to Miami to work with Tom Dowd on an album. We got so far with it. Someone had given me a book called The Story Of Layla And Majnun, which was a Persian story about being driven mad by falling in love with a beautiful, unavailable woman. I loved the name and I had the main body of a song that was obviously about Pattie. But I knew it needed something else. A motif. I realised we had something after Duane Allman came up with the riff." - Eric Clapton
https://www.uncut.co.uk/features/the-making-of-derek-and-the-dominos-layla-24633
"There is nothing I can do" line is exactly the same as the Layla riff. It's just slower and the song is in another key.
These are Clapton's words form the same link you gave, but from page 2.
Clapton: We spent a lot of time working together on the guitars and Duane was very instrumental in the development of the song. He came up with this riff that was pretty much a direct lift from an Albert King song, ‘As The Years Go Passing By’ from the Stax album Born Under A Bad Sign. It’s a slow blues and there’s a line that goes, ‘There is nothing I can do if you leave me here to cry’, and we used that.
It also says this in the article: Whitlock remembers that Clapton already had Layla when they started writing together: “He wrote that song by himself at home.” The opening riff was also there – taken from Albert King’s As The Years Go Passing By – but the song was much slower than it finally appeared. Here is the link
https://www.loudersound.com/features/the-story-behind-the-song-layla-by-derek-and-the-dominosAnother quote: “You know what? That riff is a direct lift from an Albert King song. And I don’t have to pay royalties because . . . [He hums the riff.] Hmmm, maybe I do [laughs]. It’s a song off the Born Under a Bad Sign album ["As the Years Go Passing By"]. It goes, There is nothing I can do/If you leave me here to cry. It’s a slow blues. We took that line and speeded it up.
- Eric Clapton, interview
1988
http://12bar.de/ftp/text_info/rollin_stone_interview_1988.txtMy response about the Layla riff was just to clarify that he did not actually "came up" with it. I didn't want to suggest that because of that, he was not a great artist he is.
I am not disputing the talents and achievements of Duane Allman, but to say that he, as you said, is the reason that "Layla And..." album is a masterpiece, is a bit far fetched in my opinion. And I repeat, I think you're giving him too much credit.
And we are getting a bit off topic of this thread I'm afraid.
