Question about Sigma 105mm f/2.8 EX DG OS HSM Nikon F

Not in my opinion.

A little more detail. It is a macro lens. Of course you can photograph concerts with it if the focal length fits. But that's not what it was made for. Most macro lenses have a very slow autofocus. And why should you buy a relatively slow fixed focal length instead of, say, an 85mm f1.8? If f2.8 is enough, I would recommend a 70-200. But it always depends on 1. what kind of concerts it is and 2. how far away from the stage it is. In very dark locations, I wouldn't want to shoot without an f1.4 or f1.8 fixed focal length.