The Dead have probably the biggest ups and downs on any band I can think of. When they are at their best I dont think theres any band who plays better. When they are at their worst, well, its not gonna be pretty. Im not too sure about them being out of tune. I know Ive seen shows where the sound was terrible and Ive always blamed that on their set up and the fact that some arenas and a lot of outdoor venues were just not built for concerts.
There was always a problem, IMO, with the volume of certain instruments and Ive read comments in some of their books and it appears that the blame is simply on their crew. Ive been at concerts where you literally cannot hear anything coming from a person yet you can clearly see them playing. This happened a lot to the keyboard players, at times to Bob Weir and even to Phil Lesh. Im no pro by any stretch but I think someone was doing a poor job in the set up or the mixing of the music.
I think Bob can sing, at the very least he is a great live performer when he carries a tune. I thought Brent was a good singer, I liked Vince too, but just about everyone else was up and down to me. I never liked the females in the various bands much, even the recent ones and Ive never been big on Lesh singing either. He has a very hard time carrying a tune. Jerry could sing when he wanted too, much like Dylan, but neither are obviously gonna bring the house down with stirring vocals. Still both are effective and have their moments for certain.