In terms of chords and melody, Crimson Fly has complexity on par with the typical song, having near-average scores in Melodic Complexity and Chord-Melody Tension and below-average scores in Chord Complexity, Chord Progression Novelty and Chord-Bass Melody.
Crimson Fly is written in the key of B Minor. According to the Theorytab database, it is the 5th most popular key among Minor keys and the 13rd 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 (B minor, E minor, and F♯ minor). See the B Minor Cheat Sheet for popular chords, chord progressions, downloadable midi files and more!