JE's sound was 99% size and strength of fingers, plus training in instruments other than bass that gave him a less 'root-fifth mentality' plus having to compete with Mood and Townsend, plus being a naturally curious innovator. The other 1% was the bass.
There's a lovely interview somewhere in which JE says he had to be THAT loud to be hear above Townsend, who says he had to be THAT loud to be heard above JE. There is something really magical about the Live at Leeds tone, both bass and guitars, it's utterly visceral at times, a great listen even today 👍