I quite like the sentence, but I'm not sure the time reference is requested. The way I understand it is: P. D. sang so well that the audience progressively stood up, and at the end of the 2 hours'concert, everybody was standing on their feet.
In a Western theatre, the custom is for audiences to stand up and applaud at the end if they wish to show great appreciation. It's called a 'standing ovation'.
Here, I'd say that the singing caused the audience's appreciation to grow during the two hours, and at the end they stood up.
I don't care how good a singer is, I'm not going to stand up for two hours,