OK, maybe not that extreme. But I am learning how to scream wile I sing. And it's easier than I thought. After learning how to start the technique it was really easy to pick it out from old songs that I listen to. Even heard it wile watching a Harry Potter movie over at my mom's yesterday. It's a technique that is actually very relaxing to the throat. Takes a lot of practice to get it right. To be able to hit it when you need it. If not it sounds really bad. : ) It all starts with than gravelly moan anyone can do. Think of how you would say "I really don't want to get up" wile still in bed. Then learn to work that smoothly all the way up to your highest falsetto. It's been used in rock for decades now. And it's the same technique thrash and hard core metal singers use to sing. A good example is Janis Joplin. She owned it. If you jump to 20:10 there's a great example of how this technique sounds. Her voice is not naturally gravelly. She hits the technique and lets it go like a pro.
https://www.youtube.com/watch?v=5NuZxUxHN0o&frags=pl%2CwnIt really adds some depth to what your singing. Now I just need to learn to stay in pitch. Or just scream my way out of needing to.

This is the vid that got me started,
https://www.youtube.com/watch?v=7nNba4V-lXs&frags=pl%2CwnPart two is just a commercial for their school.
Going to explore what i can find on line first. If I can't find what i'm looking for there's a book called 'The Zen Of Screaming".
The absolute one book I recommend to anyone wanting to learn REAL techniques for singing is "The Rock and Roll Singer's Survival Manual". Hands down the BEST book out there.
Don't plan on singing hard core. Just want to be able to add an aggression to the music I do.