I came across this post which claims to expose musics worst singers
While I think it proves the point that, get famous and you can get paid for something that would be buzzed off on Britain's Got Talent, I don't think some of these are the worst I've seen... or heard rather... there are many live concerts were the singing has left a lot to be desired.
A notable absence from the list as far as I am concerned though and one I would certainly put up there at the top of the list is one by Miley Cyrus
Of course it depends on your point of view. Fans will say the recordings have been doctored but I'll leave people to make up their own minds.
Reminds me of The Simpsons Boy Band episode - unfortunately I couldn't find a link to where they turned off the machine... lol.