Like JimA said, there are just so many mediocre-to-bad singers, that a lot of (instrumental) musicians like me get pretty...uh...cautious. That being said, most of my gigs these days are backing up local singers. The one I work with most is a fine singer and she's one of my best friends. But we laugh about the first time we met. I was playing a gig with an organ trio and she and another singer dropped by the club. The bandleader knew them and invited them to sit in. I was thinking, "Oh great, a couple of damn chick singers! Shit!" and apparently I was wearing those thoughts on my sleeve, because my friend remembers me giving her quite a chilly reception as she came to the bandstand. Well, she sang her ass off, and my worst fears were NOT confirmed, but I still tend to keep those shields up when facing new "chick singers".