well, it was very specific squawking, I don't know all the right terms yet. He would make a very quiet sound that was like a murmered squawk (lol) when I would have treats in his line of sight. He was a very quiet bird and so soliciting any sounds from him was a bit of a challenge. He began to try out different sounds of differing volume, and eventually tried to mirror the sounds I made. He got the most rewards when mimicking and he did learn a few words in the short time I had him
As I train a variety of animals from dogs to lizards to fish to what have you, I definitely don't have a traditional background in bird training like yall, just sharing what I found worked.
It was NOT the same as rewarding shrieking and non solicited noises. It was definitely very specific things he did that got rewarded, I was very careful not to turn my friends bird into a shrieking demon.
Mostly we worked on tricks, such as "foot" (lifts his foot), wings (when they stretch their wings vertically), flex (when they stretch their opposite foot and wing), shoulder(go to shoulder, he didn't like hands), and a variety of in the cage and on the cage positioning so we could easily do maintenance and such in his cage

He is very famous on my buddies stream for the silly tricks he learned. We were working on "hi-yah!" which was a combo of "wings" and "foot". He loved to show off his wings and tricks even without treats. They are definitely one of the smartest animals I've trained. Training him gave me a much more zealous attitude toward training my other animals. My Service dog in training made huge strides during that period as I was extra motivated
feel free to delete if you think I did it wrong and am giving bad advice admins
He definitely knew what numnums and apple meant imo, as he would get pretty upset if he said apple and I didn't immediately go get one for him XD (although that could just be me putting my inexperience on him)