The 'Run the World (Girls)' singer was apprehensive about signing up for the festival - one of the Europe's biggest - after her husband, Jay-Z's, inclusion on the 2008 bill proved controversial, but Chris helped talk her round, according to co-organiser Emily Eavis.
She told Radio Times magazine: "Chris is a bit wary of people knowing he's been so involved. I don't know why because it's actually cool.
"Chris is as loyal as they come - he'll do anything for Glastonbury. He's really an unlikely frontman. Most people are a bit more all-consumed with their own thing."
Emily said while Beyonce - who releases her new album '4' next week - has been keen to play since she saw Jay perform, they had to book her as early as possible.
Emily added: "Luckily, we spoke to Beyonce before she planned her tour this year, so she managed to put Glastonbury in her schedule, then build a European tour around it."