updated 08/29/2013 AT 2:00 PM ET
•originally published 08/31/2013 AT 2:30 PM ET
“I remember as a kid watching Frank Sinatra sing ‘New York, New York’ with his orchestra behind him,” Morrison, 34, tells PEOPLE. “The telethon is virtually an encyclopedia of what’s great in American show business.”
The actor and singer says the opportunity to perform at the telethon is “humbling,” but also inspiring.
“I don’t consider it a challenge, but rather an honor. I’m just excited to be part of a great show for a great cause,” Morrison says of the telethon, which will air Sunday (9 p.m. ET) on ABC.
Morrison is just one of the many Hollywood stars slated to take part in the iconic event, including Ryan Seacrest, the Backstreet Boys, Enrique Iglesias, Paula Abdul, Austin Mahone and country artists Luke Bryan, Darius Rucker and Lee Ann Womack.
But the truly grew thing about the telethon, Morrison says, is that it keeps the spotlight on the Muscular Dystrophy Association’s work.
“The real stars of the show are the MDA families, the kids, who are living with muscle diseases and facing challenges that many of us can barely imagine,” he says.
So what exactly will he be singing during the show? “I got my start on Broadway and I’m going to sing one of my favorites songs, from one of the greatest Broadway shows ever,” he says.
“That’s all I’m going to say, you’ll have to tune in to see it.”