Roger Waters perfoming Have A Cigar at Rock In Rio 2006.
You can hear, that he is not really singing here, it's a prerecorded backing track.
Unfortunately, the mixer messed it up, so the prerecorded vocals were mixed louder than the live vocals.

Roger Waters use prerecorded vocals in several songs live, but to be fair, he is an old man and it must be hard on your voice to be on tour