I found a cool hack for singers that tell me dont ever let me try that song again while still leaving it in their list.
I add the song to the playlist under their name, then re-title the song in the playlist
example
I Knew The Bride
to I Knew The Bride < never again > (no spaces between brackets), then right click the song - click add to \'the singers name\' songs, and walla, the song now is stored in the singers history to never try that song again and do not have to delete it
It will remain that way, unless you refresh the singer database for some reason or put it in the playlist and play it. It only affects that singers list and nothing else!
Here is a shot of the singer history