"Lawdy Mama," 1967 (outtake from Disraeli Gears, later released on Live Cream). Jack Bruce, bass; Ginger Baker, drums; Eric Clapton, guitar and vocal.
So smooth. These guys truly were the cream of the crop, each complemented the others perfectly. I love this – the perfect vocal timing, the masterful strutting beat, but perhaps most of all Jack Bruce’s expert bass playing, which supports Clapton then subtly emerges at the surface in places with something unexpected. Functional, I suppose, but never pedestrian, though I’m no expert (and yet arguably there were some cases, e.g. the famous live "Crossroads," where Bruce outplayed Clapton).
If you are somewhat familiar with Cream you may notice the similarity here to the song "Strange Brew": their producer, wanting something more trippy and pop than a white-man’s-blues rendition, put a new vocal and guitar track from Clapton over the existing bass and drum parts. From what I gather Bruce wasn’t around to supply a revised bassline and was unhappy (understandably?) with the result.
I don't know what the equivalents in painting would be to the layers in a musical piece, but I think of a great bassline as something like the imprimatura or primuersel that shows through in a painting, whether visible in transparent passages or in parts left exposed outright (see Rembrandt). In the best cases it doesn't immediately jump out and smack you in the face.
[Credit to the original posters.]