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Chords and Triads
Major, Minor, Diminished, and Augmented
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A chord is a group of notes played together, and the most basic chord in Western music is the triad. A triad uses three different pitch classes arranged in stacked thirds: the root, the third, and the fifth. Learning triads helps students understand harmony, song structure, and why some note combinations sound stable or tense. Triads appear in piano music, guitar chords, choir arrangements, and even digital music production.
A triad can be built by starting on a root note and adding notes a third and a fifth above it within the scale. In semitone terms, major and minor triads differ by the size of the third, while the fifth often stays the same. For example, a C major triad is C, E, G, and a C minor triad is C, Eb, G. Seeing the same triad on both a musical staff and a keyboard helps connect abstract note names to real sound and instrument layout.
Key Facts
- A triad contains three chord tones: root, third, and fifth.
- Major triad interval pattern: root to third = 4 semitones, root to fifth = 7 semitones.
- Minor triad interval pattern: root to third = 3 semitones, root to fifth = 7 semitones.
- Diminished triad interval pattern: root to third = 3 semitones, root to fifth = 6 semitones.
- Augmented triad interval pattern: root to third = 4 semitones, root to fifth = 8 semitones.
- Example formulas: C major = C + E + G, C minor = C + Eb + G.
Vocabulary
- Triad
- A three-note chord built from a root, a third, and a fifth.
- Root
- The root is the note that names the chord and serves as its basic reference pitch.
- Third
- The third is the note above the root that helps determine whether the triad is major or minor.
- Fifth
- The fifth is the note above the root that adds stability and helps complete the triad.
- Semitone
- A semitone is the smallest standard step in Western music, such as from one piano key to the next adjacent key.
Common Mistakes to Avoid
- Counting letter names instead of actual intervals, which is wrong because triad quality depends on semitone distance, not just note labels. Always check the number of half steps from root to third and root to fifth.
- Assuming every three-note group is a triad, which is wrong because the notes must be arranged as stacked thirds in pitch-class structure. A random cluster of three notes may not form a triad.
- Forgetting that the third determines major or minor quality, which is wrong because changing the third changes the chord type even if the root and fifth stay the same. Compare C-E-G with C-Eb-G.
- Treating inversions as different triads, which is wrong because changing the order of the notes does not change the chord's basic identity. C-E-G, E-G-C, and G-C-E are all forms of C major.
Practice Questions
- 1 Build a G major triad by note name. Identify the root, third, and fifth.
- 2 A triad has a root of D and a minor third and perfect fifth above it. Write the three notes of the chord.
- 3 Explain why C-E-G and E-G-C are considered the same triad even though the lowest note is different.