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5.4 The iii (III) Chord

cesar torruella

caroline koffke

(editor)

⏱️ September 23, 2020

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Harmonic flowchart in Major Key: iii as tonic prolongation. Image from Robert Hutchinson: http://musictheory.pugetsound.edu/mt21c/HarmonicFunction.htmlHarmonic flowchart in Minor Keys: III as tonic prolongation.

Image from Robert Hutchinson: http://musictheory.pugetsound.edu/mt21c/HarmonicFunction.htmlA name is assigned to each scale degree. Tonic, Supertonic, Mediant, Subdominant, Dominant, Submediant, and Leading Tone. The Mediant degree refers to degree 3 of any Major Scale.

The III/iii

The iii or III chord serves as a prolongation of the tonic. Some textbooks call this an expansion of the tonic as well, especially if it appears at the beginning of a phrase (I-iii or i-III.)

ALWAYS check yourself when analyzing chords and you find a iii (in major.) Think about it twice! The only place where you find iii is in a I-iii-IV progression at the beginning of a phrase.

We are using Roman Numerals to identify and analyze music. On Unit 3 we went over the harmonic functions and names for each harmony and each scale degree

A name is assigned to each scale degree. Tonic, Supertonic, Mediant, Subdominant, Dominant, Submediant, and Leading Tone. The Mediant degree refers to degree 3 of any Major Scale.

The mediant triad or iii (III in Major) is rarely used in harmonic progressions of 18th-century style, also called common practice. The mediant triad in a minor key-iii-appears more often in its role as representing the relative major key

Check for understanding:

Can you name each scale degree by memory?

1. Tonic
2. Super Tonic
3. Mediant
4. Subdominant
5. Dominant
6. Submediant
7. Leading Tone

What chords can you use to extend the tonic function?

1. In Major Keys: iii and/or vi

1. In Minor Keys: III and/or VI