I once was able to "cure" my Charlie from screaming with "Hello" conversations. A simple Hello is much more enjyoable to listen to than his constant screamings. However, repeatedly saying hello back and forth gets tiring for me! If I didn't reply to him, he'd scream then say hello again.
I don't mind when Charlie screams first thing in the morning because that's when food arrives. I'd be grumpy too, if I was hungry!
Charlie was considered the loudest in his foster home (as compared to some amazons, macaws, green cheek conures and a couple of rosellas!) and he's still the loudest here! Besides him, there are four cockatiels and a bourke parakeet. Needless to say, their presence makes no difference! Although, I do believe that if Charlie had a buddy he could get along with, he might be quieter! But then, I could end up with two noisy birds, too!