It's official: Pretty much every major artist who released Christmas music this year will be a part of NBC's Christmas in Rockefeller Center, airing December 2 at 8 p.m. ET/PT.The list of performers this year includes Kelly Clarkson performing with her "Under the Mistletoe" duet partner Brett Eldredge, plus Goo Goo Dolls, Pentatonix, Gwen Stefani, Dan + Shay, Tori Kelly, and Meghan Trainor performing with the group Earth, Wind & Fire, who appears on her album A Very Trainor Christmas.In addition, Dolly Parton and Jimmy Fallon will sing a duet, and there will be other performances by Leslie