I have also watched this before and it's one of my favourite cockatiel videos!
Another big favourite of mine is Kame-chan, he whistles the chocobo theme song and the victory tune from the Final Fantasy games.
I've also seen this video before. There is nothing cuter than tiels singing with their wings raised like this and with such cheerful expression. My boy tiel also does this routine to get my attention and it always works. I think they know to use this gesture to disarm us.