Dolly Parton is showing her holiday spirit a few months ahead of schedule by lending her vocals to a soon-to-be-released album by the band Chicago.

Parton was at the studio when the band was recording the upcoming album 'Chicago XXXIII: O Christmas Three,' and agreed to lend her legendary voice to the song 'Wonderful Christmas Time.' The song is one of 14 traditional songs that Chicago recorded in their own style for the October 4 release.

"Dolly Parton was at the studio doing something else, and her producer came in to say hi,'" original Chicago band member and trumpeter Lee Loughnane tells Taste of Country with a laugh. "Then he said, 'Let me go get Dolly,' and she agreed to sing. It was completely off the cuff. Dolly said, 'I came in to say hi, and the next thing I know, I'm singing!'"

The new Chicago album also includes guest cameos by legendary guitarist Steve Cropper, perhaps best known for his work with Booker T and the M.G.'s, gospel/R&B singer Bebe Winans and the band America.

Although Parton only sings a few lines in the song, the sound is "unmistakeably Dolly. She sounds just great," says Loughnane, adding, "She is a nice lady, who really has her head together and seems to do all she can to help other people."

Parton is currently on the European leg of the tour behind her just-released album 'Better Day,' and wasn't available to comment about her work with Chicago.

In talking with Taste of Country a few weeks ago, though, Parton said she maintains an early-to-bed, early-to-rise regiment that allows her to fully relish her career. When told of her comments, Loughnane agrees that Parton is a true professional.

"We don't party anymore," he says, speaking for both his band and Parton. "This is our lives. We're all still around unlike many, many other people in this business [because] we've learned to treat our careers as an important part of our lives, not something that is just going to last two to five years."

For more information about the holiday release, go to Chicago's website.