But the two musicians got over their differences last Monday as they came together in a studio in Los Angeles to record an album to raise money for Haiti.
Many artists turned out to show support, including: the Jonas Brothers, Miley Cyrus and Justin Bieber who sand together "We are the World" by Michael Jackson.
In the 1980's this song was used to help raise money for children in Africa. NOw it is being used for Haiti.
Here we have for you a few photos of this amazing recording session. All of the musicians leaving their bad vibes outside and working together for a good cause.
