Singing over complicated bass lines

I started playing bass in 1962. After wasting most of my formative years as a civil servant, I turned professional and toured the American Bases in France. I was the only one in the band that could be let loose on the mic, but I didn't realise how difficult it was playing bass and singing. Black Is Black was suggested by the band, recorded by Los Bravos, took me quite a while to synchronise the both. Next was Band Of Gold by Freda Payne, a difficult one. Took me years to be able to split my brain in two, one side concentrating on the bass line, the other on singing. It takes a hell of a long time. Now I play in a group doing covers like I Shot The Sheriff, now that's a tester (The Eric Clapton version) and Crosby, Stills, Nash & Young covers.