In terms of chords and melody, Impossible has complexity on par with the typical song, having near-average scores in Chord-Bass Melody and below-average scores in Chord Complexity, Melodic Complexity, Chord-Melody Tension and Chord Progression Novelty.
Impossible is written in the key of F Minor. According to the Theorytab database, it is the 8th most popular key among Minor keys and the 20th 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 (F minor, B♭ minor, and C minor). See the F Minor Cheat Sheet for popular chords, chord progressions, downloadable midi files and more!