Unit 4: Triads and Seventh Chords

This study guide summarizes the Unit 4 concepts from the provided photos. It is a paraphrased review, not a transcription of the textbook.

Core Idea

Triads are the basic chords of tonal music. They grow out of the intervals of a third and a fifth above a root, and they can appear in root position or inversion. Seventh chords add a dissonant seventh above the root and therefore introduce a stronger need for resolution. The unit also begins to connect chord labeling with musical texture, harmonic progression, and voice leading.

Triads

A triad is a three-tone chord built from a root, third, and fifth. When the root is the lowest tone, the chord is in root position. The four basic triad qualities are determined by the quality of the third and fifth above the root:

Major and minor triads are consonant and are the most important triad qualities. Diminished and augmented triads contain dissonant intervals and are less stable.

Diatonic Triads in Major

Each scale degree of a major key can support a diatonic triad. The pattern is:

I major
ii minor
iii minor
IV major
V major
vi minor
vii diminished

Roman numerals identify chord roots by scale degree. In the common mixed-case system, uppercase numerals show major triads, lowercase numerals show minor triads, and a small circle marks diminished triads.

Triads in Minor

Natural minor produces a different pattern of triad qualities:

i minor
ii diminished
III major
iv minor
v minor
VI major
VII major

Minor-key music often raises scale degree 7 to strengthen motion to tonic. This changes the quality of chords that contain 7, especially V and vii. With raised 7, V becomes major and vii becomes diminished, matching their dominant-function forms in the parallel major key.

Raising scale degree 6 can also change chord quality, but those forms occur more selectively. The practical principle is that the expected motion to tonic often determines whether scale degrees 6 and 7 appear in their natural or raised forms.

Triad Inversion

A triad is inverted when a chord member other than the root is the lowest tone:

• Root position: root in the bass
• First inversion: third in the bass
• Second inversion: fifth in the bass

Inversion depends only on the bass, not on the order of the upper voices.

Figured-bass symbols name intervals above the bass:

• Root-position triad: 5/3, usually omitted
• First-inversion triad: 6/3, usually written 6
• Second-inversion triad: 6/4

Root-position triads are more stable than inversions. First- and second-inversion sonorities may arise either as actual chord inversions or from melodic motion over a stationary bass.

Figured Bass

Figured bass is a shorthand system that uses numbers and accidentals above a bass line to indicate intervals above the bass. It comes from continuo practice, where performers realized harmonies from a bass and figures.

Important conventions:

• Key signatures apply to figures.
• Accidentals next to figures alter the indicated interval above the bass.
• An accidental by itself usually affects the third above the bass.
• Figures specify intervals above the bass, not the exact spacing of upper voices.

Roman numerals and figured bass answer different questions: Roman numerals name the chord root and scale degree, while figured bass names intervals above the bass and indicates inversion.

Chords from Melodic Motion

Not every 6 or 6/4 sonority should be understood as a structural inversion of a triad. Some arise because a voice moves melodically above a stationary bass, creating temporary sonorities such as 5-6 or 6-5. In those cases, labeling every sonority with a Roman numeral can exaggerate its harmonic independence.

Seventh Chords

A seventh chord contains a root, third, fifth, and seventh. The seventh above the root is dissonant and normally resolves downward by step. Seventh chords historically grow out of melodic dissonance, especially passing motion such as 8-7 resolving onward.

Important seventh-chord qualities include:

• Major seventh: major triad plus major seventh
• Minor seventh: minor triad plus minor seventh
• Dominant seventh: major triad plus minor seventh
• Diminished seventh: diminished triad plus diminished seventh
• Half-diminished seventh: diminished triad plus minor seventh
• Minor-major seventh: minor triad plus major seventh

The dominant seventh is the most important seventh chord because it occurs on scale degree 5 in major and in inflected minor and has strong dominant function.

Seventh-Chord Inversion

Seventh chords have four positions:

• Root position: root in the bass, figured as 7
• First inversion: third in the bass, figured as 6/5
• Second inversion: fifth in the bass, figured as 4/3
• Third inversion: seventh in the bass, figured as 4/2 or 2

As with triads, Roman numerals name the root while figured bass indicates the bass position.

Texture and Structure

In note-against-note texture, voices move in the same rhythm and the sonority is usually made only of chord members. Figurated texture enlivens a chordal framework through quicker motion. Figuration may arpeggiate chord tones or add nonchord tones such as passing tones, neighboring tones, suspensions, anticipations, and appoggiaturas.

Harmony and Voice Leading

Harmony concerns relationships among chords. Voice leading concerns the simultaneous motion of melodic lines. They are inseparable in practice: moving lines create chords, and chord progressions imply line-to-line motion.

The fifth relationship is central to tonal harmony. The dominant is the scale degree and chord a fifth above tonic, and the tonic-dominant relationship is one of the basic organizing forces of tonal music.

Memory Targets

• Know the four triad qualities and their interval formulas.
• Memorize diatonic triad qualities in major and natural minor.
• Understand how raised 6 and raised 7 change minor-key chord qualities.
• Identify triad inversions by the bass note and figured bass.
• Distinguish Roman numerals from figured-bass symbols.
• Recognize when 6 and 6/4 sonorities may arise from melodic motion rather than independent chord inversion.
• Know common seventh-chord qualities.
• Know seventh-chord inversions and figures: 7, 6/5, 4/3, and 4/2.
• Remember that the chordal seventh normally resolves downward by step.
• Distinguish note-against-note texture from figurated texture.
• Explain the difference between harmony and voice leading.