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Session Length
~19 min
Adaptive Checks
17 questions
Transfer Probes
9
Harmony, triads, and chords form the vertical dimension of music, describing how notes sound simultaneously to create richness, tension, and resolution. This topic covers the construction and identification of the four triad qualities (major, minor, diminished, augmented), the five common seventh chord types (major 7th, dominant 7th, minor 7th, half-diminished 7th, fully diminished 7th), chord inversions and figured bass notation, and the system of Roman numeral analysis that labels diatonic chords by their scale degree and function.
Understanding chords is essential for harmonic analysis, composition, arranging, and improvisation. Every chord in a key has a specific function -- tonic, predominant, or dominant -- that drives the harmonic motion of a piece. Learning to build, identify, and analyze chords in all keys provides the foundation for voice leading, chord progressions, and the more advanced chromatic harmony topics covered in later AP Music Theory units.
Whether you are a pianist voicing jazz chords, a guitarist reading chord symbols, or a theory student analyzing a Bach chorale, mastery of triads and seventh chords is the gateway to understanding how harmony works in Western music.
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A triad is a three-note chord built by stacking two thirds above a root note. The four triad qualities are major (M3+m3), minor (m3+M3), diminished (m3+m3), and augmented (M3+M3). Each quality has a distinctive sound character.
Example: C major triad = C-E-G (major 3rd + minor 3rd). C minor triad = C-Eb-G (minor 3rd + major 3rd). C diminished = C-Eb-Gb. C augmented = C-E-G#.
A seventh chord adds a fourth note a third above the fifth of a triad. The five common types are: major 7th (M3+m3+M3), dominant 7th (M3+m3+m3), minor 7th (m3+M3+m3), half-diminished 7th (m3+m3+M3), and fully diminished 7th (m3+m3+m3).
Example: In C major: Cmaj7 = C-E-G-B, G7 = G-B-D-F (dominant 7th on scale degree 5), Am7 = A-C-E-G, Bm7b5 = B-D-F-A (half-diminished on scale degree 7).
A chord inversion occurs when a note other than the root is the lowest-sounding pitch (bass note). Root position has the root in the bass. First inversion has the third in the bass. Second inversion has the fifth in the bass. Seventh chords also have third inversion with the seventh in the bass.
Example: C major in root position = C-E-G. First inversion = E-G-C. Second inversion = G-C-E. The notes are the same but the bass note changes the sound and function.
Figured bass uses numbers below a bass note to indicate the intervals above it, specifying chord inversions. Root position triad = 5/3 (often no figures). First inversion = 6/3 (written as 6). Second inversion = 6/4. For seventh chords: root = 7, first = 6/5, second = 4/3, third = 4/2 (or 2).
Example: A bass note C with figures 6/3 means play a first-inversion triad: the notes C (bass), E (third above), and A (sixth above), forming an A minor chord in first inversion.
Diatonic triads are chords built using only the notes of a given key. In Roman numeral analysis, uppercase numerals indicate major triads and lowercase indicate minor triads. A degree symbol indicates diminished and a plus sign indicates augmented.
Example: In C major: I (C), ii (Dm), iii (Em), IV (F), V (G), vi (Am), vii-dim (Bdim). In A minor (natural): i (Am), ii-dim (Bdim), III (C), iv (Dm), v (Em), VI (F), VII (G).
Diatonic seventh chords are four-note chords built on each scale degree using only notes from the key. Each scale degree produces a specific seventh chord quality, creating a unique set of sounds for major and minor keys.
Example: In C major: Imaj7, ii7, iii7, IVmaj7, V7, vi7, vii-half-dim-7. The V7 (dominant seventh) is the most important for establishing tonality because it strongly resolves to I.
Every diatonic chord serves one of three harmonic functions. Tonic chords (I, vi, iii) provide stability and rest. Predominant chords (IV, ii) create momentum toward the dominant. Dominant chords (V, vii-dim) create tension that resolves to the tonic.
Example: The progression ii-V-I (Dm-G-C in C major) moves from predominant to dominant to tonic, creating a satisfying sense of departure and return that is the foundation of tonal harmony.
Chord quality is determined by the specific combination of intervals stacked from the root. By knowing the interval structure, you can build any chord quality from any root note without memorizing every individual chord.
Example: To build a dominant 7th chord on any root: stack a major 3rd, then a minor 3rd, then another minor 3rd. From Bb: Bb-D (M3), D-F (m3), F-Ab (m3) = Bb7.
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