Darlene Love on final "Late Show" Christmas performace

Over the past 28 years on "Late Show with David Letterman," one voice has ushered in the holiday season -- music legend Darlene Love singing "Christmas (Baby Please Come Home)." On Friday night, Love takes the stage on "Late Show" for the 21st and final time.

"The energy when you walk into that building to do this show ... that kind of energy is there all the time. I have no idea what they're going to do this year," Love said.

It was that "something special" Letterman spotted in the '80s when the singer performed in a New York City club with "Late Show" music director Paul Shaffer.

"Two nights later David asked Paul, 'Are you still doing that show downtown?' And he said, 'Yes, yes.' He said, 'That song, that Christmas song that that girl sings in the show is fantastic!'" Love recounted.

"She was killing it every night, and he was blown away and he asked her to come on the show," Shaffer said.

Love thought it would be a one-time deal but kept getting invited back again and again.

"After five or six years of doing that on the show, they started calling me the Christmas queen because everybody loved that Phil Spector Christmas album," she said.

Over the years, she's performed with everyone from an Air Force chorus to a flying saxophonist.

Her voice has stayed consistent.

"That's Paul Shaffer, he is such a genius," Love said. "In 28 years that this year I'll be doing that show, we've changed keys maybe four times ... And then you see the hairstyles - Jesus, keep me near the cross!"

"One thing we've learned is that it doesn't matter what we do because she's going to come out and just wail," Shaffer said.

"You know what, I haven't been this excited in so long, I think I got about three hours sleep last night," Love said.

Just like good songs, just like the holidays, even the best things sometimes have to come to a close.

"I'm trying not to think about it because I want to be able to sing great, and I can't sing and cry," Love said. "But when the song ends, it's probably when I'm going to get very emotional because it is the last time we're doing that song after 28 years. That's unheard of."

The "Late Show" is keeping details of Friday's performance under tight wraps, but Love sent CBS News a picture of her gearing up for her big night: