There's bad and there's awful.

One person at a certain venue obviously wanted to sing but protested that she couldn't. I persuaded her to sing and she was right, she couldn't. After going throught this scenario several times, she took singing lessons an improved dramatically.

Then there was this other person at an open mic. She was dressed to the nines, could play her guitar and could sing in tune. BUT, she had written some songs in her chosen style, very long songs I might add. She started off and was very dreary, halfway through her first song (about five minutes into it) she made a mistake and started over. Her three songs took about half an hour and she was dreadful.

So it isn't only being able to play and sing.