Being a musician, I know what it is like to practice with a near-perfect mix and volume. But the acoustics change when the auditorium has more people in it. What was plenty loud an hour ago will typically need boosting.Further, live music feeds on itself. If a song is really nailing it, it is very easy to play with greater intensity/volume. This serves to throw off the mix. Thus, if the bass player gets too strong (perhaps from just really getting into the music), the guitars may turn up in an attempt to reclaim the appropriate mix. The sound man, assuming he has good ears, now realizes that the vocals are getting drowned out by the music, so he ups the vocals! And we're off to the races!Lastly, few Church of God sound men (I use the term advisedly) know very much about mixing sound. I knew of one guy who came from a reserved, Baptist background who was put in the sound booth of a Pentecostal church. DISASTER! Pentecostal worship IS more exuberant--or should be!--than the worship in other churches. It will almost CERTAINLY be louder due to the greater enthusiasm that is often exhibited. This guy, the ONLY thing he knew about sound was to TURN IT DOWN! Everything seemed too loud for him.This demoralized the band. We were practicing and doing our best, only to later be told that the, say, drums could barely be heard (and the drummer was by far the most accomplished musician on the stage!).Run it all through the board, you say? Yeah, and what if Mr. I-Want-Us-To-Be-More-Like-the-Baptists is in the sound booth? Long and short of it, I didn't practice with the singers, hone my skills, and make the effort to turn up...only to not be heard. If I'm not heard, I'm not playing. Not because I'm some great musician, but because it's foolish to prepare for no reason. No one is blessed or benefited from seeing silent musicians.With an Aviom system and headphones, I can make sure I hear myself. But I didn't come to just hear myself. I came to be a part of the performance. If I find that the music is poorly mixed, instruments cannot be heard half the time, etc., yeah, I'm out. I know of one church that has a guy attending that used to mix sound for Clint Brown. Do they use him? Nope. Instead, they use people who have NO background of mixing sound. They simply do not care about their sound. They have a sizable church that has a good spirit, but as for excellence in sound, they don't have any drive in the direction.Yes, they could just turn everything down, but then the mix is lost, people can't be heard, and so it goes.Only those churches that have high-caliber sound men and instruments through the system (coupled with an in-ear monitor or such) usually get the sound right.