My approach to concert photography has always been that I should stay invisible and inhearable and inaudible for the performer and for the audience. In order to document a concert you usually need to take very few photos as their further use is very limited. I applied the same principle during the guitar concert of professor Štěpán Rak in one of the local concert halls. While I usually prefer zooming in and out with my legs, concerts are usually the place where I use zoom lens, even with an extender so that I could stand in the back. While the angle is similar, one or two photos are usually enough for the news and the camera resolution is enough to get a vertical or horizontal crop.
And most importantly, the concert was wonderful.