As unlikely as it may seem, TV talent show American Idol is now into its 21st series. That's more than CSI: Crime Scene Investigation. Or ER. Or even Lassie.
Over the years, rock music has frequently taken a back seat on the show as the judges lean towards pop, r&b and country music, but occasionally there's a breakthrough. Former Axium singer David Cook won in 2008, and 2014 winner Caleb Johnson is currently performing with Meat Loaf's old backing band Neverland Express.
