Generate travelleng matte from a nearly-white bright background?
The problem that you're going to have with this is that the colour of the screen is too similar to colours in the foreground. If you look at the levels on the highlighted part of the drummer's face they're very similar to the levels on the edges of the screen, and a similar colour, same for the drum skins and the pattern on his shirt. I had a go in AE with no success using keylight, colour range key and even extract, but nothing works. So a clean matte is going to involve lots of work rotoscoping.

One thing you might get away with, depending on your background content is to put it below the original layer, and set the original layer's transfer mode to darken. If your background layer is darker than the foreground it will show through, so as long as it's darker than the screen but lighter than the performers it will composite ok. You might help things along with some masks on the performer's faces and the other light areas, and you may get a bit of blending, but it might be good enough, without spending years roto-ing.