Ed Sheeran wrote his song for The Hobbit from the "perspective of being a dwarf".
The singer-songwriter panned the track I See Fire for sequel The Desolation of Smaug, which is out this month.
Ed was instructed by director Peter Jackson to focus on a particular part of the movie when writing the song and the musician also tried to get into the right mindset.
"I've never been a dwarf, but I've wrote a song from the perspective of being a dwarf," he told MTV News.
"Peter said, 'Focus on the last ten minutes. That's what the song needs to reflect.' He said, 'Write a song that takes the audience by the hand and leads them from Middle Earth back into reality.' So, yeah, I tried to do that."
Lyrics in the heartfelt piece include the lines 'If this is to end in fire/ Then we shall all burn together/ Watch the flames climb high/ Into the night/ Calling out 'father'/ Stand by and we will/ Watch the flames burn auburn on the mountain side'.
Ed was treated to a special preview of the finished feature before the world premiere. When he attended the star-studded screening, the 22-year-old admits he became so engrossed in the movie, his own song came as a surprise to him.
"I actually forgot my song was in the film," he sheepishly admitted. "I'm such a Tolkien and Peter Jackson fan, I was watching the film just assuming that was the premiere to watch the film. I was watching it and then the song came on and I was like, 'Oh, yep. That's why I'm here. Cool.' But I was enjoying it that much, I forgot. "