Alright, so I'm now the vocalist for the band I'm in (called For Retaliations, if anyone's curious). They were looking for a vocalist, and I was chosen only because of my never-ending confidence. Everyone else has already practiced and prepared, so the only one left is me. Since I'm new, I haven't really memorized the lines yet, and it's made worse by the fact that while I sing on-stage a lot, I haven't really sung in a metalcore voice before. It's a little embarrassing, but I can work with it. Once I'm ready, we're gonna perform, but until then...
Well, I have to learn how to sing harsh.
I can do it, but it quickly tires me, and apparently I'm not loud enough even with a mike. A vocalist from another band (formerly metalcore too, not anymore) gave me the advice to cut a lemon in half and keep the juices above my throat for about a minute, which he said will soften the strain and help me scream at full power. But this isn't what I've learned from the internet, which have told me that acidic juices only worsen your throat.
Should I follow his advice, or should I do something else? Also, the band's hoping to perform in about three more weeks. Would that be enough time to master the voice?
Three weeks is plenty of time. I was the vocalist of a black metal band all throughout high school, so I'm relatively familiar with harsh vocals. I've never heard about the lemon thing, but I would often drink water and soda while practicing/performing. The water will help soothe your throat so it doesn't get sore while screaming. The soda, at least for me, would give the saliva towards the back of my throat this kind of sticky feeling, which resulted in really raspy/gargly vocals. It helped me achieve the sound I wanted without straining my vocal chords and throat too much.
Just make sure that you scream using your diaphragm. From the sound of it, you're screaming from your throat and vocal chords alone. That'll cause your "screams" to come out around the volume of a speaking voice and not really a scream (not to mention, it'll wear our your throat quicker and damage your voice). Make sure you're bringing up air from your diaphragm; it'll help raise the volume of your screams. It sounds a bit confusing, but just imagine you're about to yell really loudly. Take a deep breath, and let the screams out.
It's all about practice. Don't wear yourself out, but practice a few times daily--even if that means just screaming to yourself in the shower or something while no one else is around. That's how I learned. Just remember that pain is typically nature's way of telling you that you're doing something wrong. Vocalists didn't learn their techniques from a text book. Just practice different techniques until you find one that is comfortable for you and produces the sound you're looking for. Good luck!