I've been hearing him my whole life, since I started listening to the AM radio in the late '60s. Cream was probably still together. I think the first riff I learned on the guitar was Sunshine of Your Love and one of the first albums in my collection was the Heavy Cream comp.
He was a busy, melodic bassist and what a singing voice, all quite unique. The only band I actually got to hear was one with Billy Cobham at the Capitol Theatre in Passaic, NJ when they were touring the I've Always Wanted To Do This album in December '80.
A sad day for music, RIP Jack.