I've never smelled another bird so here's my opinion.
When we first got Buddy his feathers were very dirty, like he hadn't bathed in a year. The green looked a dingy brown at the ends. Not caked, just dull & IDK, yucky. He stunk too, bad stink. It took regular misting & baths to convert him to AN normal Amazon smell. When he's wet he has a musty smell that eminates from his neck area in the back... I try to soak this area when he's getting a bath. When he's dry, it pretty much becomes null.
He also seems to have a smell that eminates from the beak & stomach/crop area within. This always seems to smell like the last food he eats. If I give him chamomile in his morning sprouts, it smells of chamomile. If I then give him peppers @ lunch... I'll smell peppers when he's on my shoulder. I guess it's our equivilant of a burp.
They say that the vets & experts don't know where these smells come from. Maybe, we've concluded these areas because Buddy lives on us. I don't know that I'm right, its just my family's opinion that these are the where's. I'm not positive that it is the actual where....