When I was a kid, someone gave us a cockatiel that had been trained to talk. The bird would say the usual stuff like 'pretty bird' and 'hello', and from time to time would whistle the song "Dixie". This was back in the days when 'Teach your bird to talk" recordings were on LP- apparently there was a scratch on the record, and the bird would get hung up on the same phrase for minutes. The bird would literally whistle dixie for hours.
My awesome pet cockatiel was named Poopy, after saying it a few hundred times it lost original meaning, so when I see a cockatiel I just think ITS A POOPY!
Once I had a box of cockatiel seed with a big photo pf a happy cockatiel's head on it and Poopy began worshipping it as a god, he would stare at it for hours and try to feed it and please it, when I put my hand nearby he screamed and protected it. I threw the box away. Poopy was awesome. I have so many Poopy stories.
Unfortunately their voices are not pleasing to the ear.