I'm watching them play right now. How do these vocalists do that guttural thing? Doesn't seem humanly possible.

It's actual shit. The furthest thing from slam metal. I used to book some dudes who watched them grow from a rap metal/nu metal band and start that dumb slam shit. Start here. https://m.youtube.com/watch?v=-JYFgoaEeaQ

Cognitive and NJ Bleed opened up. A very ignorant evening.

Don't know those acts.