From the outside, Westend Recording Studio is an unassuming building in a quiet neighborhood just across State Line Road in Kansas City, Kansas. But inside, insulated by walls of foam, there's a hardcore noise rock band recording session.
Mantooth has been a producer and audio engineer for about 15 years, and he's spent the last two at Westend.
Last fall, he launched a project, offering free studio time for local metal, punk rock, alt-rock, doom bands and more. Within two days of getting the word out, he heard back from 45 bands.
Five months later, he released "Amplify KC" Volume 1, a compilation featuring everything from the straight rock n' roll of The Runaway Sons "Same Bed," to the stoner doom crush of Keef Mountain's "Conjuror."
In general, heavy music is a genre that developed out of other forms of rock. It's evolved over the years, and the subgenres abound.
"You can't even label heavy bands anymore, because you end up with some long sentence of 'post-grunge, post-punk, hardcore, shoegaze, sludge metal.' You can't even define it, it just all blurs together," he says.
But the basic rules remain the same.
"Everything's got to be big," he says.
And Mantooth did his best to represent as many variations as he could in an 11-track album. Where Hyborian's "The Head and the Sword" is melodic and harmonic with a distinct build, Sharp Weapons' "Brilliant Normal" is intense and in your face right away — hardcore punk rock carried by screaming vocals.
"It's an adrenaline rush," says Fritz, host of The Pit, the heaviest hour on Kansas City's 98.9 The Rock.
When Fritz leaves the studio every night, it takes him at least two hours to decompress from the intense, powerful, aggressive music. But, he says, it's like therapy.
"You get it out, then you feel good," Fritz says. "When you meet most metal bands they're usually the most mellow dudes in the world, because they get that aggression out on stage."
These days, with a trimmed beard and a Baldwin KC hat, Justin Mantooth appears to be a pretty "mellow dude."
But, a late '90s teenager out in the Kansas suburbs, he was the ultimate punk rock kid in middle America. With multi-colored hair, chains and piercings, he worshipped third wave punk and ska bands like Rancid and Nirvana.
"To be punk rock, when you do take showers, you've got a lot of crap you gotta take off and put back on," he says. "You get older and it just gets ridiculous. I can't have 70 bracelets on every day, it's like, what, am I suiting up for battle or something?"
Despite his exterior, he's still punk at heart. His moral compass, he says, is 100 percent punk rock. This prevailing mindset, and his evolving musical interests, is what motivated him to feature Kansas City's heavy scene in "Amplify KC."
"There's actually a very diverse scene here," he says. "The average band in KC is really tight, really good at what they're doing, because they're not trying to get famous, they're not trying to put together the perfect band. People play for the love of it here. And that results in good bands."
Andrea Tudhope is a reporter and producer for KCUR 89.3. You can find her on Twitter @adtudhope.