I was told I should check this thread out.
First, Twangirl is in the know. She is omnipotent as far as the 9:30 is concerned. As to the way things can go wrong with sound, I can give you another 20 if you would like, 30 if I spend some time thinking. Pretty much, anything and everything can and will go wrong, and there is so much going on that you can not have 100% confidence that everything will work right every night. Bands and their crews are well aware of this and deal with it. Why do you think they have spare guitars, snares, and amps?
Here is the path from his microphone to the FOH board at the 9:30:
Mic
cable
sub-snake
patch panel/splitter
house snake
FOH
Not that simple a path, and often the cables are reused and just patched down at the splitter so if that has not been changed then you get no vocals (or whatever was in that channel). Sometimes you can quickly find the channel that the mispatched line is coming out and run it there until you correct the problem. To keep this from happening you often will see a line check before the band comes out. And even then something can go wrong in that 5 minutes. Since it was not a patch problem, all you can do is find the problem and fix it ASAP. Not an easy thing to do.
I work sound at the 9:30 on occasion (was not there that night), and wonder what you mean by vocals lost in a sea of garbled sound and the bass so high or low, blah blah blah. What shows was this the case at, what vocals, when? Details are needed if you wish the problem to be fixed. For all I know you were standing in the one spot that sucks (right against the stage), and there is nothing anyone can do to fix the problem. So, give some information and we can see what the problem might be and how to correct it.
That said, many times it is the engineers with the bands, and sometimes their whole PA that is in the club. We do very little with the actual sound those nights, and still people will bitch that we did something wrong.
