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The Allman Brothers song featured in the 1973 horror classic "The Exorcist" is "Dreams". Penned by Gregg Allman, this haunting track plays a pivotal role in the film's climax, amplifying the intensity and psychological impact of the scene. With its slow tempo, melancholic chords, and Gregg Allman's raw, emotive vocals, "Dreams" perfectly complements the movie's unsettling atmosphere, leaving a lasting impression on the audience.