About the Elton John and Billy Joel concert... PLEASE ANSWER!!!!?

Okay, so my dad says he'll PROBABLY take me to the Elton John-Billy Joel concert at the HP Pavillion on Nov. 7th. I was wondering... Is it like, Elton sings one of his songs, Billy sings one of his songs. Or... what? And is it a really memorable expierence? I'm only 13... But I LOVEEEEEE Elton. I've been listening to him ALL MY LIFE! Billy's good too. Thanks :) PLEASE answer!!!