OK, I've been doing BM style vocals for about a year and a half now and people have asked me how I do it. I have always replied that I really can't explain the technique, it just happens, and it isn't painful.
However, I recently found this
What is Vocal Fry?
Glottal or Vocal Fry is the term used by some to describe lowest part of the voice. It is effectively a toneless "rattle", rasp or roughness produced by the vocal cords at the lower end of the range which is often used as an effect in rock singing. Click Here for an audio example of spoken glottal fry at Lions Voice Clinic website.
at
http://www.vocalist.org.uk/voice_registers.html
Also, I was in the studio recording vocals for my technical thrash band "Carnage" the other day. I started off using this mega expensive condenser microphone that the college had just bought and the vocals sounded completely shit, really airy and hollow. I switched to my usual Sure SM58 and things sounded much better. So this got me thinking about my whole technique and how much a microphone can colour the sound.
So I will attempt to explain the basics of high-pitched vocal technique.
Start by saying "O, A, E" out loud. You should notice that before the sound of the vowel actually comes out of your mouth, there is a very small kinda "uhh" sound. It's very small and you wont notice it unless you're listening for it, it's part of the attack of the sound. This is basically vocal fry. Try saying the same three vowels again but this time, don't let the main body of the sound start, stay in the vocal fry at the beginning. It should sound a little like a forced whisper. This is the basic technique as far as I can tell. To make it into a useable vocal style, you'll have to apply some force from the diaphragm (just kinda push from your stomach) to project the sound. It should sound raspy and evil
Once you've got the basics then you should develop the technique yourself, I can't really tell you how to improve because everyone is different.
How do you know you're doing it right? Well, it shouldn't hurt at all, if it hurts, you're doing it wrong, anyone that says it should hurt is wrong and you'll damage yourself if you follow his or her advice. When I do it, I sometimes feel a slight "tightness" in my head, especially on 20+ second screams, if you're not careful you can get light-headed and even pass out, and you won't look very evil or "kvlt" if you feint like a pussy. This happens because you're not letting enough oxygen get to your brain as it's all being used up from screaming, passing out is your bodies defence against this as you should breathe normally when you pass out. As far as I know this is not dangerous at all, you'd pass out before you could actually cause brain damage or anything. Just remember to breathe in the right places and you should be ok.
This "tightness" in the head is actually a sign that you're doing it right. How hard you push from your stomach and how much air you use is one of the hardest things to get right. I find that for recording you need a really loud headphone mix so that you have to really belt out the vocals to be heard. Live is usually ok because you have the volume of the rest of the band to contend with. If the PA and levels are set up properly then you shouldn't have too much trouble finding the optimum pressure for the vocals.
EQ'ing and the kind of Microphone you use also play a nig part in the sound. If you enhance the treble and take off most of the mids and bass, then the vocals sound more "blackmetalish" whereas boosting the mids can give you a more "messy" sound that's better for thrash or grindcore, if you ever get a chance to record your vocals, make sure you play around with the equaliser settings. If you have subtones in your screaming voice, they can be eliminated with EQ, or boosted to give you a more "tortured" vocal sound live the vocals on War by Burzum. While I'm on the subject, subtones are both useful and a pain in the ass. You should try to practice controlling subtones as much as possible, you can go for nearly all subtones and a bit of vocal fry to get that "varg vikernes" sound I was talking about or you can go for mainly vocal fry and some subtones to get a sound like Alexi from Children of Bodom or Petri Lindroos from Norther. Most vocalists try to get rid of subtones completely though, but you should remember that they have their uses and can be used to great effect to add feeling or enhance certain parts.