In terms of chords and melody, Speak Now 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.
Speak Now is written in the key of G Major. According to the Theorytab database, it is the 3rd most popular key among Major keys and the 3rd most popular among all keys. Major keys, along with minor keys, are a common choice for popular songs. The three most important chords, built off the 1st, 4th and 5th scale degrees are all major chords (G Major, C Major, and D Major). See the G Major Cheat Sheet for popular chords, chord progressions, downloadable midi files and more!