What is the name of that 80's music animated short where a group of aliens are doing a symphony while an astronaut watches, then takes them away in a technologic made bubble/

I'm not sure if you are talking about Interstella 5555, Daft Punk's MTV for their Discovery album.

I've heard about a popular orchestra of the 80's
Called Rondo Veneziano

They released a series of music videos in the 80's
Each with the similar theme of a ruined/flooded Venice-like cityscape with a chrome Android classical orchetra playing amist the ruins.

La serenissima