Two of the best websites for info are:
Disney World - The Largest Unofficial On-Line Guide to Disney World, Walt Disney World and
AllEars.Net - The Unofficial Disney Vacation Planning Guide - Walt Disney World, Disneyland and Disney Cruise Line
Concerts are held during the Flower & Garden and Food & Wine Festivals. Flower & Garden are starting off The Who, followed by Gary Lewis & The Playboys, and the last concert will be Allen Parsons Project. Expect groups such as Herman Hermits, Paul Revere & The Raiders, Monkees, etc. Nothing is finalized yet for the Flower & Garden (Eat to the Beat).
If you go during Food & Wine Festival you can see groups such as Starship starring Mickey Thomas, Go-Gos, Air Supply, Manhattan Transfer, Wilson Phillips, The Pointer Sisters, Boyz II Men, Smash Mouth.