Thanks for your comments Viginia Tam but I think you have actually missed my point which was the fact that people were allowed in while performers were singing rather than waiting till the applause at the end of a song/tune. If a sign was available to say "please do not enter till you hear applause" people could then come in and get to available empty seats before the performer started their next song/tune,thus keeping any disruption to a minimum. I hope
this clarifys my comment.