I think it's really the bird. There are Amazons that come to my local pet bird club and sing like that, although their repertoire isn't quite that extensive. Amazons are some of the most talented talkers/singers in the parrot family.

Amazons are often considered the best talkers in the bird family, competing mostly with Greys.

That bird has some nice vibrato, I'm jealous!

Looks like the bird singing ect....
Some are so much vocal than others..
Years ago I knew a parrot who could hold
a short conversation with people.. was amazing.

Wow...I've never heard a bird sound like that before.