Some are more vocal than others. And I think males are more vocal than females. That's from what I've heard at any rate. I just have boys, so no girls to compare to, but my guys never shut up! LOL
Have you tried playing music for Cheeko? That usually gets them singing.
I don't think it's anything to worry about..just some like to chatter more than others. And it doesn't necessarily mean he's not comfortable yet...just not a blabber mouth
Try some different kinds of music and see what he likes. I wouldn't go for keet sounds because that just might confuse him in to thinking there are other keets around and he'll wonder where they are and try to call out to them.
My 2 get louder with more people around.. or say everyone is laughing etc too. I think they want to join in..add their 2 cents. LOL