Just to add to this thread ... one of the most incredible displays of someone who could play and sing together to the point of a highly-developed skill was Sting! I saw The Police in their heyday during their "Ghost in the Machine" tour during the 80s. Sting was playing the bass part to the song "Spirits In the Material World" and also dancing around on the stage while he was singing the the lead vocal. It sounded awesome and his bass part was spot on. I didn't realize how difficult this surely was until I'd learned the guitar and bass part a few years later. It was hard enough to do that part without having to do any singing at all. I couldn't believe that someone could play that bass part and sing at the same time.

--Jim