In terms of chords and melody, Holly Jolly Christmas has complexity on par with the typical song, having near-average scores in Chord Progression Novelty and below-average scores in Chord Complexity, Melodic Complexity, Chord-Melody Tension and Chord-Bass Melody.
Holly Jolly Christmas is written in the key of C Major. According to the Theorytab database, it is the most common key in all of popular music. See the C Major Cheat Sheet for popular chords, chord progressions, downloadable midi files and more!