The former Eurythmics singer will perform the theme song for "The Lord of the Rings: The Return of the King," the final chapter in the mammoth screen adaptation of J.R.R. Tolkien's trilogy about mythical hobbits, elves, wizards, dwarves and humans in a battle of good against evil.

The soundtrack, due out Nov. 25, will feature highlights from Howard Shore's score and Lennox's song "Into the West."

"It has been a fascinating experience to be a very small part of this vast jigsaw puzzle entitled 'The Lord of the Rings,"' Lennox said. "The dedication and commitment to the project is awesome in every way."

Shot simultaneously by director Peter Jackson, the films starring Elijah Wood, Ian McKellen, Viggo Mortensen, Cate Blanchett and Liv Tyler have been released one a year since 2001.

"The Return of the King" opens Dec. 17.