Unit 3: Music Fundamentals III: Triads and Seventh Chords
AP Music Theory: 49 practice questions with detailed explanations.
Unit Study Guide
Executive Summary
Chords stack thirds. Triads and seventh chords come in qualities, invert over the bass, and get labeled with Roman numerals and figured bass.
Triads
Three notes stacked in thirds. Quality from the intervals: major = M3 + m3; minor = m3 + M3; diminished = m3 + m3; augmented = M3 + M3. C major is C-E-G; A minor is A-C-E; B diminished is B-D-F.
Seventh chords
Add a seventh above the root. Dominant 7th = major triad + minor 7th (G-B-D-F in C major). Major 7th = major triad + major 7th. Minor 7th = minor triad + minor 7th. Half-diminished = diminished triad + minor 7th; fully diminished = three minor thirds (G#-B-D-F).
Inversions
Root position: root in bass. First inversion: 3rd in bass (figured 6). Second inversion: 5th in bass (6-4). Seventh chords add third inversion: 7th in bass (4-2); first and second inversion seventh chords figure 6-5 and 4-3; root position figures 7.
Roman numerals
Numerals name the scale degree; case shows quality: I, IV, V major; ii, iii, vi minor; vii diminished in major. In minor: i, iv minor; V major in harmonic minor. Inversions add figures (I6, V6-5).
Exam traps
Diminished = two minor thirds, augmented = two major thirds. Figures name intervals ABOVE THE BASS. vii diminished functions as dominant, not predominant.