Musicians on a mission

Justin Timberlake  (Marcel Antonisse / EPA)

Kanye West  (Matt Dunham / AP)

Rihanna  (RICHARD DREW / AP)

The Police: Andy Summers, Sting, Stewart Copeland  (D. Ross Cameron / AP)

Kelly Clarkson  (Peter Kramer / Getty Images)

Akon  (Roger Kisby / Getty Images)

John Legend  (Evan Agostini / Getty Images)

Joss Stone  (Getty Images / Getty Images)

Al Gore and Melissa Etheridge  (Myung J. Chun / LAT)

Red Hot Chili Peppers: Flea and John Frusciante  (Kevin Winter / Getty Images)

Metallica’s Robert Trujillo  (Paul Hawthorne / Getty Images)