AP Music Theory: The Mediant Chord - Your Ultimate Review 🎶

Hey there, future music maestros! Let's dive into the world of the mediant chord (iii/III) and make sure you're totally prepped for the AP exam. This guide is designed to be your go-to resource, especially when you're doing that last-minute review. Let's make this click!

1. Diatonic Harmony Refresher 🎼

Before we zoom in on the mediant, let's quickly recap our diatonic chords and their functions. This is crucial because the mediant's role is all about context. Remember, we're building a solid foundation here!

• Tonic (I/i): Our home base, provides stability.
• Predominant (ii/ii°, IV/iv): Creates tension, leads to the dominant.
• Dominant (V/V, vii°): Heightens tension, strongly pulls to the tonic.
• Submediant (vi/VI): Weak predominant or tonic prolongation.

2. The Mediant Chord (iii/III) 💡

Okay, let's talk about the star of the show: the mediant chord. It's the chord built on the third scale degree and is often the trickiest to grasp. Here's the lowdown:

• Major Key: iii (minor triad)
• Minor Key: III (major triad)

2.1. Mediant as a Tonic Prolongation

• The mediant is often used to expand or prolong the tonic, especially at the beginning of a phrase.

• Think of it as a detour that keeps us within the tonic's gravitational pull.

• Common progressions: I-iii or i-III

2.2. Mediant as a Weak Predominant

• The mediant can act as a very weak predominant, usually followed by stronger predominant chords.

• It's like a 'pre-predominant' chord.

• Typical progressions: I-iii-IV or i-III-VI

• If both iii and vi are used, iii usually comes first.

2.3. Mediant as a Dominant (Disguised!) 🤯

• Here's a twist: in first inversion (iii⁶), the mediant can sound like a dominant chord with a non-chord tone.

• The third of the mediant resolves down to the second scale degree, creating a dominant feel.

• Progression: iii⁶-V (or III+⁶-V in minor, where the leading tone is raised)

• This is a contextual analysis point, not a new notation.

2.4. Expanding the Tonic with Mediant & Non-Functional IV

• A common way to expand the tonic is using I-iii-IV-I (or i-III-iv-i) progression.

• The IV chord here is non-functional, meaning it's not creating a strong subdominant pull to the tonic.

• Melody often moves stepwise down (8-7-6-5 scale degrees).

• Doubling the root in I and iii, but doubling the third in IV is common practice.

• Ending with I⁶ is also common.

3. Mediant in Minor Keys: Tonicization and Modulation 🗝️

• In minor keys, the III chord is the tonic of the relative major.

• This is crucial for understanding tonicization and modulation.

• Tonicization: Borrowing chords from another key for a short time.

• Modulation: Establishing a new key as the 'home' key.

• Composers often modulate to the relative major in minor-key pieces, especially in sonata form's development section.

• If you see lots of III, VI, and VII chords in a minor piece, you might be in the relative major key!

Understanding modulation is key for analyzing longer musical forms. Pay close attention to the function of chords in the new key.

4. Putting It All Together: Harmonic Progressions 🧩

• Remember the T-PD-D-T phrase structure.

• Use the mediant in its various roles: tonic prolongation, weak predominant, or even a disguised dominant.

• Don't be afraid to experiment with inversions for smoother voice leading.

🦜 Polly's Challenge: Here's a sample T-PD-D-T progression using all seven diatonic chords:

I - iii - vi - ii⁶ - V - vii°⁶ - I

5. Final Exam Focus 🎯

Okay, you've made it this far! Here's what to focus on for the exam:

• Mediant Functions: Tonic prolongation, weak predominant, disguised dominant.
• Tonic Expansion: I-iii-IV-I progressions.
• Modulation: Especially to the relative major in minor keys.
• Contextual Analysis: Always consider how chords function within the phrase.
• Voice Leading: Smooth transitions are key to good harmony.

6. Practice Questions

-   Correct key identification: 1 point
-   Correct Roman numeral analysis for each chord: 1 point each (5 points total)
-   Correct function identification for each chord: 1 point each (5 points total)
-   Total: 11 points

Alright, you've got this! Go ace that exam, and remember, music is about understanding and feeling, not just memorizing. You're going to do great! 🎉