Spanish composer Javier Navarrete had worked on numerous Spanish language films, including Del Toro's earlier The Devil's Backbone, before finally getting his first Oscar nomination and worldwide recognition with Pan's Labyrinth. Although many of his original pieces were cut from the film, you can listen to the soundtrack in its entirety here.
Just don't listen to it if you're afraid of the dark.
The film's score is based around the idea of a fairy tale. It has a light, childish quality, making it sound at times like a lullaby. The opening track, "Long, Long Time Ago," features the soft humming of a maternal voice. In a similarly calming tone, the score also features tracks inspired by the sound of a music box, like the opening of the film's second track, "The Labyrinth," which sounds like something a young child could fall asleep to.
But, like the story, Navarrete's score quickly becomes very dark and ominous. Though it still retains the romance of the classical, orchestral sound, the score reflects the darkening of the film from exciting fairy tale to a world of monsters both fantastical and human. The track "Not Human" begins with some foreboding strings, eerie buzzing sound of woodwinds, and even some choral chanting, before blowing up into full scale horror with the brass section.
The score may be based on lullabies…but by the time we've made it through the movie, it sounds more like a nightmare.
Of course, all of these different moods and motifs aren't just thrown into the film willy-nilly. The track "The Moribund Tree and the Toad," fits together many of the movies musical tones. At around 3:16 we get the pounding strings and clashing percushion as we watch Vidal and his men ride out to find the rebels, but at 3:36 this melds into some tinkling piano as Ofelia reads from her book and makes her way through the sunny fields toward the tree. But, upon reaching the tree, the music turns foreboding. Not in a violent, militant sort of way like it felt previously with Vidal's men, but a slower, more grandiose, melancholic sound that matches the change in lighting from the bright forest to the dark shadow of the toad's home.