Unit 3 Study Notes: Building, Labeling, and Understanding Triads and Seventh Chords

Triad

A three-note chord built by stacking thirds above a root; its chord members are root, third, and fifth (in any order or with doublings).

Root

The starting note of a chord, identified by conceptual stacking in thirds; it names the chord even if it is not the lowest-sounding pitch.

Bass

The lowest-sounding note of a harmony; it may or may not be the chord’s root (because chords can be inverted).

Stacked Thirds

A way to find a chord’s root by rearranging its notes into consecutive third intervals (e.g., C–E–G–B).

Triad Quality

The triad type determined by the sizes of the intervals root→third and third→fifth (i.e., two stacked thirds).

Major Triad

A triad with a major 3rd from root to third and a minor 3rd from third to fifth; equivalently, major 3rd + perfect 5th above the root.

Minor Triad

A triad with a minor 3rd from root to third and a major 3rd from third to fifth; equivalently, minor 3rd + perfect 5th above the root.

Diminished Triad

A triad made of a minor 3rd plus a minor 3rd; it contains a diminished 5th above the root and tends to sound unstable.

Augmented Triad

A triad made of a major 3rd plus a major 3rd; it contains an augmented 5th above the root and tends to sound tense.

Altered Fifth

A fifth that is not perfect (diminished or augmented), often increasing tension (common in diminished and augmented triads).

Diatonic Triads in a Major Key

Triads built using only notes of the major scale, producing the pattern: I major, ii minor, iii minor, IV major, V major, vi minor, vii° diminished.

Leading Tone

Scale degree 7 in major (or raised 7 in minor) that strongly tends to resolve up by step to tonic; often forms diminished chords (vii° or viiø7).

Harmonic Minor

A minor-scale form with raised scale degree 7, commonly used to create a stronger dominant (V or V7) and leading-tone chord (vii° or vii°7).

Seventh Chord

A four-note chord built by stacking thirds to include a seventh above the root (a triad plus one more third).

Seventh Chord Quality

The chord type determined by (1) the triad quality (root–third–fifth) and (2) the quality of the seventh above the root (major, minor, or diminished).

Major Seventh Chord (MM7)

A major triad plus a major seventh above the root (e.g., C–E–G–B).

Dominant Seventh Chord (Mm7)

A major triad plus a minor seventh above the root (e.g., G–B–D–F); commonly functions as V7 in tonal harmony.

Minor Seventh Chord (mm7)

A minor triad plus a minor seventh above the root.

Half-Diminished Seventh Chord (ø7)

A diminished triad plus a minor seventh above the root (e.g., B–D–F–A in C major: viiø7).

Fully Diminished Seventh Chord (°7)

A diminished triad plus a diminished seventh above the root; differs from ø7 by having a smaller (diminished) seventh interval.

Root Position

A chord position in which the root is in the bass; for triads, figured bass is 5/3 (often left unmarked), and for seventh chords it is 7.

First Inversion (Triads)

An inversion with the third in the bass; figured bass 6/3, usually shortened to 6.

Second Inversion (Triads)

An inversion with the fifth in the bass; figured bass 6/4.

Figured Bass

A shorthand indicating the intervals above the bass note (not above the root); common figures include 6, 6/4 for triads and 7, 6/5, 4/3, 4/2 for seventh chords.

Roman Numeral Analysis

A system that labels chords by scale-degree root in a key, showing quality (case and symbols) and inversion (figures); chromatic alterations are shown with accidentals placed before the numeral.