well, i see a lot of people asking how to growl and get deeper, so i'm going to post how i do it.

growling
put your hand on your throat
clear your throat (the mm-hmm sound), you should be able to feel which muscles tense and which loosen with your hand.
breathe into your stomach (your chest should move very little)
replicate the tensions you felt before and push the air from your stomach upward and speak
tips when you're growling, try pointing your tongue slightly upward so it's almost touching the front of your palate, you can experiment with different tongue positions for different sounds
also once you've got the basic tensions right you can try altering them slightly to produce the desired sound
and lastly: when you're growling don't sing, think of it as pitched speaking.

deeper
tense your abs, kind of like you're taking a shit
widen your throat a little, or a lot depending on how deep you want to go
shape your mouth into an O shape, this will make you go much deeper but you will barely be understandable


side notes
if it starts to hurt/tickle consistently try to almost move your throat away from the spot that's hurting/tickling and it should clear up.
if you're new it may start to hurt after a while, just stop for a while, maybe drink some milk and start up later when you feel your good to go. push your limits slowly!
having a lot of spit can help you growl, to increase spit control replicate what you would do when gargling water without the water until you get a gargling sound.

i hope this helped at least some people. if anyone has anything to add you're welcome to do so

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Cheers mate. I will be attempting what you advised tomorrow when no one is home .