Something I haven't mentioned that can seriously effect the way the music sounds is the production. Black Metal production in the early days (and in some bands of today) is often very badly done, due to lack of funds to pay for big production houses. Then you get the muddy production, which is clear but it sounds muddled and not so great. Clean production is something you'll find on Power/Heavy Metal songs and select extreme artists. It doesn't matter to me really, as a wise man once said: