FILE - Willie Nelson smiles backstage during the 25th anniversary Farm Aid concert in Milwaukee on Oct. 2, 2010. (AP Photo/Jeffrey Phelps, File)

FILE - Signage for the "12-12-12" concert is displayed on the Madison Square Garden jumbotron, Tuesday, Dec. 11, 2012, in New York. (AP Photo/John Minchillo, File)

FILE - Willie Nelson entertains the audience while performing at the Farm Aid Concert in Camden, N.J. on Saturday, Sept. 30, 2006. (AP Photo/Tim Larsen, File)

FILE - Jesse Ed Davis, center right, a guitarist of Kiowa and Comanche ancestry, performs with George Harrison, left, formerly of the Beatles, at the Concert For Bangladesh at Madison Square Garden in New York on Aug. 1, 1971. (AP Photo/Jim Wells, File)

FILE -David Bowie, front left, and Bob Geldof, right right, appear at the end of the London part of the Live Aid famine relief concert at Wembley Stadium in London on July 13, 1985. (AP Photo/Joe Schaber, File)

FILE - Singer Willie Nelson speaks during a news conference on July 28, 1995, in Louisville, Ky., where it was announced Louisville had been selected as the site for Farm Aid's 10th anniversary concert. (AP Photo/Ed Reinke, File)

FILE - George Michael, from left, concert promoter Harvey Goldsmith, Bono of U2, Paul McCartney, concert organizer Bob Geldof and Freddie Mercury of Queen join in the finale of the Live Aid famine relief concert, at Wembley Stadium, London on July 13, 1985. (AP Photo/Joe Schaber, File)

FILE - Willie Nelson performs at Farm Aid 2002 in Burgettstown, Pa., Saturday, Sept. 21, 2002. (AP Photo/Jasmine Gehris, File)