In 2004 the journal Logopedics Phoniatrics Vocology published a study of what its four Swedish authors called dist tones, the distortion rock singers lay over a note on purpose, filmed with a high-speed camera looking straight down the throat, and the footage settled the oldest question in the rehearsal room: how do metal singers scream night after night and still have a voice on Sunday? The noise was not coming from the vocal folds. It was coming from the tissue above them.
The singer and researcher who led that work, a rock vocalist turned voice researcher, was Daniel Zangger Borch, and with the voice scientist Johan Sundberg beside him he watched the true folds keep a clean, regular vibration while the soft structures just above them, the ventricular folds and the rim of the aryepiglottic folds, flapped against the airstream and shredded the smooth wave of the note into grit. Two sources, one sound. That is the scream.
A rifleman would recognise the trick. A muzzle brake is a collar of slotted steel screwed onto the end of a barrel, and the blast of powder gas chasing the bullet out slams into its baffles and is thrown sideways through the ports, so that the round leaves at full speed while the recoil that would have smashed back into the shooter's collarbone is bled off into the air. The violence leaves the mouth. The true folds are the shoulder, and they are spared.
How do metal singers scream? Above the folds, not with them
Start with the anatomy, because every technique is a choice about which piece of it to rattle. The true vocal folds, two bands of muscle and mucous membrane in the larynx, make the pitch. Just above them sit the ventricular folds, often called the false folds, which close when a person lifts something heavy or coughs, and above those the aryepiglottic folds run from the arytenoid cartilages to the epiglottis like the rim of a funnel. A clean note uses only the first pair. A scream borrows the others.
The first lesson most coaches teach is therefore not to scream at all but to get the false folds out of the way. The American singer and researcher whose method gave that manoeuvre its name was Jo Estill, and Estill Voice Training calls it retraction, the widening above the folds that happens in a silent laugh. A singer who can retract at will can then choose how much constriction to let back in, and where. Control comes first. Noise is added after.
Complete Vocal Technique, the Copenhagen method, files the metal noises as effects laid on top of a clean mode rather than as separate voices: distortion, creak, rattle, growl and grunt, each with its own structure doing the rattling and each needing a healthy clean sound underneath it. A scream is a clean note with something rattling on top of it. That condition is the one amateurs skip, and the one that keeps singers working.
A scream is a clean note with something rattling on top of it.
Air is the other half of the trick, and it runs against instinct. A good scream uses less breath than it sounds as if it does, held back under steady pressure from the belly and the ribs while the throat stays open above the folds, so that the grit is made by resonance and placement rather than by force. Push harder and the noise gets smaller. Shouting is loud; screaming is shaped.
The high scream and the rasp
The high metal scream is mostly a belt, the bright chest-dominant voice driven up into the top of the range, with distortion added on top of it and the vowel kept narrow and forward. The Canadian singer whose screams tore across the title track of Skid Row's second album in 1991, at the top of a belt that should not have survived a world tour, was Sebastian Bach, and "Slave to the Grind" is a primer in the high scream: a clean pitch underneath, a coat of rattle over it, and the vowel pinned in place while the drums lay concrete round it.
Listen to where the pitch sits in that song. Bach hits notes a tenor would sing clean, and the distortion never lets go of them, which is the whole point: the rattle rides on the note, and the note is doing the carrying. Take the note away and the rattle has nothing to stand on. It collapses into a cough. Copy the rattle without the note underneath it and the voice lasts about a week.
The rasp works lower and closer to speech. The Louisiana singer who had sung high and clean on Pantera's Power Metal in 1988, and who then rebuilt himself around a bark with the false folds fully engaged, was Phil Anselmo, and on Vulgar Display of Power, released by Atco in February 1992, Pantera built whole songs around that bark. Nothing had been lost. Something had been added on top.
"Mouth for War" is the rasp at work in the arena. Anselmo pitches each line like a shouted order across a parade ground and then lets the false folds rip the edges off it, the syllables staying sharp enough to follow while the grit takes the skin off every consonant. The bark sits low in the chest voice, close to the pitch of speech, which is why it can run through a whole set without climbing into danger. The words are still there. That is technique, not luck.
Fry, false cords and the growl
Below the rasp lie the extreme techniques, the ones the heavier branches of the family run on. A fry scream starts from vocal fry, the low crackle the voice makes at the bottom of its range when very little air is moving, and then feeds pressure into it until the crackle turns into a sustained, lacerating hiss. A false cord scream drives the ventricular folds themselves into vibration, and the growl, lowest and most guttural of all, recruits the aryepiglottic folds as well. Each puts the rattle in a different place, and each has its own price.
One technique runs backwards. The inhaled scream, drawn on the in-breath rather than the out-breath, gave grindcore and later deathcore their squeals, and most coaches treat it warily because it dries and chafes the folds faster than anything sung on the way out. It sounds like nothing else. It also wears a voice down faster than anything else.
The physics of the growl is the strangest part. The Japanese researcher who filmed growl singers in 2004, working with a team at the Health Sciences University of Hokkaido, was Ken-Ichi Sakakibara, and his group found the structures above the folds vibrating at a fraction of the pitch below, often half of it, which puts a second, lower pulse under the note and makes one throat sound like two. The full catalogue of those voices, register by register, is set out in the types of metal vocals.
Howl, howl, howl, howl! O, you are men of stones.
William Shakespeare, King Lear
Wear, rest and the throat that goes
Every rifle barrel has a throat, the short tapered stretch just ahead of the chamber where the bullet first bites into the rifling, and every hot round sandblasts it a little further, until after a few thousand shots the lands are worn back, the bullet jumps before it bites and the groups open up across the target. A singer who screams from the true folds wears out the same way, one night at a time. The groups open. The note goes.
The damage has names a laryngologist would recognise, nodules, polyps and bleeding into the fold, and all of them come the same way, from the true folds slamming together harder and more often than they were built for while none of the onslaught is handed up to the structures above. A scream made above the folds can be repeated for decades. One made in them is spent in months.
Why the voice had to climb so high and hit so hard in the first place, over two stacks of amplifiers and a hall full of people shouting back, belongs to that part of the history. How it survives the climb is a question of anatomy, and the anatomy has been filmed.
