I never realized until a few years ago just what a heavy hitter he already was, long before the formation of Zeppelin.
He was an accomplished composer and arranger, and one of Mickey Most's "first call" session men.
He had a huge impact on Donovan's breakout sound ("Sunshine Superman", "Mellow Yellow", "Hurdy Gurdy Man") and he and Page had been collaborating for years already when Zeppelin was formed.
Just never knew how much more than a session bassist he was.
He even did the string arrangement for "She's A Rainbow" (!)
Bet by that time the "Ramble On" part was just another little ditty that came naturally to him.
I'd hazard most don't realize just how important an element of the Zeppelin sound he really was.
Not to preach to the converted, but for those who want to know more, his Wiki page:
https://en.wikipedia.org/wiki/John_Paul_Jones_(musician)