Producer extraordinare Rick Rubin is working on a compilation of peace songs, according to MTV.com.  Rubin says he asks most artists he works with to record a song about peace, and has stockpiled quite a few over the years.  Rubin says he decided to compile the songs after the 2003 Grammy Awards, at which he claims artists were warned not to speak out against the Iraqi war.

"Before they went out to either present awards or play, artists were threatened that if they mentioned the Iraq war, they would not be invited back to the Grammys, ever, under any condition," Rubin told MTV.com. "This really upset me, and it made me realize that while a single artist can talk about a subject on his or her own, it's rare for artists to get together and talk about a single idea. The Grammys were a place where a lot of artists gathered together who probably had similar feelings about the war and probably could have spoken with some unity, but that right was taken away from them."

Rubin says Audioslave, the Red Hot Chili Peppers, System of a Down, Sheryl Crow, and the late Johnny Cash will all appear on the compilation. Cash covered the '60s political Folk song "Last Night I Had the Strangest Dream" before he passed away last fall.

The compilation currently has no title or release date.