In terms of chords and melody, Happy - Woodkid Sad Remix is more complex than the typical song, having above average scores in Chord Complexity, Melodic Complexity, Chord Progression Novelty and Chord-Bass Melody.
Happy - Woodkid Sad Remix is written in the key of B♭ Minor. According to the Theorytab database, it is the 11st most popular key among Minor keys and the 23rd 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!