The iii (III) Chord in AP Music Theory: Full Explanation
Understanding the iii (III) chord is essential for mastering harmony in AP Music Theory. This chord plays a unique role in both major and minor keys, offering subtle yet powerful harmonic color. In this guide, we’ll break down its construction, function, and usage in chord progressions.
What Is the iii (III) Chord?
The iii chord (pronounced “three chord”) is the mediant chord built on the third scale degree of a major or minor scale.
- In major keys, it’s a minor triad (e.g., E minor in C major: E-G-B).
- In minor keys, it’s an augmented triad in harmonic minor (e.g., E major in C harmonic minor: E-G#-B) or a major triad in natural minor.
Function of the iii Chord
The iii chord has a tonic function, meaning it shares two notes with the I chord and can sometimes substitute for it. However, it’s less stable than the tonic and often acts as a passing chord between I and IV or vi.
Common Progressions Featuring the iii Chord
- I – iii – IV (Soft, flowing motion)
- iii – vi – IV – V (Common in pop and jazz)
- I – vi – iii – IV (Plagal motion)
Why Is the iii Chord Underused?
Unlike V, IV, or vi, the iii chord doesn’t have a strong pull, making it less common in cadences. However, it adds harmonic richness when used effectively.
Examples in Popular Music
- “Let It Be” (The Beatles) – Uses I – iii – IV – I
- “Creep” (Radiohead) – Features I – III – IV – iv
Conclusion
The iii (III) chord may not be as prominent as V or IV, but its subtle harmonic color is invaluable in music composition. Understanding its function helps in writing smoother progressions and analyzing complex harmonies.
Want to master AP Music Theory? Keep practicing chord functions and experiment with the iii chord in your progressions.
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