There's yet another version of "Sing" that we'll listen too soon.
This is what Annie Lennox posted on her own blog about it yesterday:

"While I was in LA I managed to make a new version of Sing which is different from the album track... and will be made available (hopefully) next month.
It's exactly what I wanted Sing to be."

Annie is also performing Sing herself at concerts on her US tour which is taking place right now.

Source: Madonna Tribe