My thanks to them!
When all was ready...I made the proper introduction of our Group and encouraged the crowd to join in by singing, jumping or clapping or whatever as we entertained them.
As soon as the song ended, I signalled for the technical soundman who appeared...telling him the problem.
If I had not been sharply alert no one would have been any wiser. But the performance quality would have been adversely and seriously affected.
I looked at the crowd and assessed that we were with them and they were just warming up to us after our first song.