Tinted lacquer! If you stain beech, 9/10 it will have areas really dark and areas that won't take the stain at all.. best thing to do is strip it back, get the grain all looking nice and even and give it a nice thick coat of varnish!!
It doesn't have to be cheap boring old varnish.. check these out:
http://www.rothkoandfrost.com/tinted...uitar-lacquer/