Willie Nelson and Harry Connick, Jr. have teamed up to record a Christmas single to accompany their new festive movie When Angels Sing.

The pair wrote the new track for the closing credits of the movie, which debuted on Sunday night (10Mar13) at the South by Southwest festival in Austin, Texas, where the film is set.

The film also features Lyle Lovett, Kris Kristofferson and Dale Watson, among the other notable singing Texans who perform Christmas songs on camera.

The castmates were given the option of singing one of their own Christmas songs or one from a list of festive favourites - Kristofferson opted to sing co-star Nelson's Pretty Paper.

Connick, Jr., who stars in the film, admits it was difficult to take a day off when he heard who would be performing on set.

He tells Billboard.com, "I was on the set a lot... It was an amazing experience to check out these people... I was starstruck."