In terms of chords and melody, Canon in D - Variation in Phrygian has complexity on par with the typical song, having near-average scores in Melodic Complexity, Chord-Melody Tension, Chord Progression Novelty and Chord-Bass Melody and below-average scores in Chord Complexity.
Canon in D - Variation in Phrygian is written in the key of D Phrygian. According to the Theorytab database, it is the 6th most popular key among Phrygian keys and the 56th most popular among all keys. The D Phrygian scale is similar to the D Minor scale except that its 2nd note (E♭) is a half step lower. Chord progressions in Phrygian often rely on the major chord built off of this 2nd scale degree (E♭ major) which gives the key its distinctive sound. See the D Phrygian Cheat Sheet for popular chords, chord progressions, downloadable midi files and more!