Night mode will let you take pictures with 'plenty of light' but at the expense of lower shutter speed; in a concert, this means a blurry mess of moving lights and dancing people. If the stage is well lit, try 'Sports Mode' for really instant moments (but if the stage is not well lit, it'll end up being a dark shot). I'd stick to Auto mode and just play with exposure and ISO values (remember, to be able to adjust ISO settings you must turn AntiShake off)
I've always said that when a manufacturer comes up with a camera (preferably a phone one) with a "Concert Mode" that actually worked, I'd go and kiss the developers.