My biggest bigmouth Roo is the Barred Rock, Rocky.I have both those breeds and they are all very loud and vocal.
Not sure why, but that boy can certainly project! His crow is very loud. My other Roos, Wyandotte, Buff Orpington, Ameracauna & RIR all crow, but they aren't as loud as Rocky. Ameracaunas have a higher pitch but they don't crow a lot. My Buffs have a nice deep tone. The Wyandottes and RIRs are in between, not high pitch not real low. The ones that crow alot throughout the day are my Barred Rock & RIRs. I know when they see a fox or hawk, as ALL will start raising a ruckus, Roos & hens, crowing & clucking at the unwelcome intruder. I love when I let them out each section at a time in the mornings, each will do a few good morning crows. My 1 Ameracauna Roo runs out, jumps up on top of the gazebo, and belts out 1 high pitch crow, then jumps back down on the ground so I can pet him. So funny! I love them all so much!