The final strains of the Toronto Film Festival belong to Celine Dion and longtime collaborator Diane Warren.

Dion has recorded “Unfinished Songs” as the end-credits tune for “Song for Marion,” which closes the fest Saturday night at the Roy Thomson theater. Written by Warren, who’s been nominated six times for an Oscar but never won, “Unfinished Songs” is among more than a dozen collaborations with Dion, including “Because You Loved Me.”

“We go way back and I think we’re a good combination, particularly for this song,” Warren told Variety. “She had done her show from 7:30 to 9:30 that night and then recorded between 11 p.m. and 4 a.m. That’s why Celine is Celine — she really has an amazing work ethic.”

Warren said “Unfinished Songs” fits well with “Song for Marion,” a music-based dramedy starring Terence Stamp, Vanessa Redgrave and Gemma Arterton. Pic centers on a grumpy elderly man whose wife persuades him to join an unconventional local choir. The Weinstein Co. is handling domestic release.

Cutting Edge Group CEO Philip Moross, who is producing alongside Ken Marshall, brought a rough cut of the film to Warren, who wrote the song and sent it to Dion. It’s the first feature production credit for Cutting Edge, which has provided music services for more than 200 films.

“As a connoisseur of great movie songwriters, my dream has always been to work with Diane Warren,” Moross said. “What Diane was able to do with her work on ‘Song for Marion’ was to find the heart of the movie and put that heart into a beautiful chorus for Celine. It was amazing to witness.”

Four-year-old CEG has gained notice by ponying up the money for scoring, clearances and music supervision in a film; it then recoups from such sources as soundtrack and sheet-music sales, licensing and royalties from international ticket sales and TV deals. Earlier this year, it closed a multi-picture slate deal with Endgame Entertainment and entered into an agreement last month with Megan Ellison’s Annapurna Pictures.

CEG has invested in over 200 films, most notably “The King’s Speech,” in exchange for music publishing rights. CEG’s films at TIFF include the opening night selection “Looper,” “Song for Marion,” “End of Watch,” “Seven Psychopaths,” “Imogene” and “Writers.”

As for Warren, she hopes that “Unfinished Songs” may lead to that elusive Oscar.

“I’m a six-time loser,” Warren said, “so maybe this is my lucky seventh.”