In terms of chords and melody, Guile's Theme has complexity on par with the typical song, having near-average scores in Chord-Melody Tension and Chord-Bass Melody and below-average scores in Chord Complexity, Melodic Complexity and Chord Progression Novelty.
Guile's Theme is written in the key of C Minor. According to the Theorytab database, it is the 3rd most popular key among Minor keys and the 9th most popular among all keys. Minor keys, along with major keys, are a common choice for popular music. The three most important chords, built off the 1st, 4th and 5th scale degrees are all minor chords (C minor, F minor, and G minor). See the C Minor Cheat Sheet for popular chords, chord progressions, downloadable midi files and more!