-- occurs in the first minute of this scene.
You don't even have to listen to the song that comes next. It's just the implications of that scene.
Look at it this way. You're a blues player. You're playing a concert to a packed house which presumably you've done hours of painstaking rehearsing and spent mention years of practicing on your instruments. Suddenly, a group of complete strangers burst onto stage obviously confused and having no idea where they are.
I would not blame you for being angry at these people. I would, however, be somewhat confused if your demand was that these people, who for all you know have no musical experience whatsoever, sing a blues number and refuse to let them leave until they do.
There could only be only one reason for that behavior. That, over years of playing, you have gradually come to believe with a zeal reserved only for cult leaders that it is you duty,your God-given moral obligation, to do one thing and one thing only: Make sure that not one person --- NOT! ONE! SINGLE! SOLITARY! PERSON!--- leaves that nightclub without singing the blues.
I guess what I'm saying is it must really suck to be the janitor there.