I've shot lots of concerts and one thing I always do is avoid the side of the mic with the singer's hand. In other words, if they are holding it with their right hand, get on their left so the hand doesn't block your view of the face/mouth. In this case, he is holding the mic with both hands and his left is blocking his mouth. Concert photography is difficult and that makes it a great excuse to use all kinds of techniques. I do it just for the fun and practice time.

Good luck! :)