Cockatiel birds singing from Brazil
The application even allows the screen to be blanked to save battery life!

We are going to post some whistles for Cockatiels, which will be divided by football teams, popular songs, cartoons and movies. This will make it easier to get the songs for Cockatiels you like the most. To teach your Cockatiel to sing, just let your pet bird listen to the song, that is, let the whistle play for 20 to 30 minutes for 3 to 5 times a day, so that it learns, remembering that only males can reproduce well the sounds. To teach correctly, do not let the corners play straight, it will hinder your Cockatiel to learn.

I leave the application running 2 or more times a day near your cockatiel and in a very few days they will be repeating with beautiful whistles.