Building Major and Minor Triads

After this lesson, you will be able to build a major or minor triad above a given root, spell its root–third–fifth correctly, verify its interval formula, and play six named triads at the piano.

A triad uses three alternating letter names

A root-position triad contains a root, third, and fifth. Starting on C, choose C–E–G. The alternating letters form two stacked thirds on the staff. C–D♯–G may sound enharmonically close to C–E♭–G, but it breaks the required letter pattern: D-sharp has letter name D, so it forms an augmented second above C, not the third of a C triad.

The root names the chord, but it does not have to be the lowest pitch in every performance. This lesson uses root position to make construction visible. Inversions will change the bass without changing the chord's three pitch classes in Order 39.

Two checks lead to the same answer

A major triad has M3 from root to third and P5 from root to fifth, so its generic formula is M3 + P5. C major is C–E–G: C–E spans four semitones and C–G spans seven. Viewed as stacked thirds, it is M3 followed by m3.

A minor triad has m3 from root to third and still has P5 from root to fifth, giving m3 + P5. C minor is C–E♭–G: C–E♭ spans three semitones and C–G spans seven. Its stacked thirds are m3 followed by M3. Lowering only E by one semitone turns C into Cm while C and G remain fixed.

Use both checks: correct root–third–fifth letters and correct semitone distances. Counting keys alone can produce bad spelling; alternating letters alone can overlook an accidental.

Symbols are not voicings

The bare symbol C ordinarily means a C-major triad. The suffix m in Cm means C minor. A chord symbol supplies root and quality, but it does not dictate octave, rhythm, fingering, articulation, or whether the notes are blocked or rolled. A specific distribution of those chord tones is a voicing.

In the middle register, right-hand 1–3–5 may be comfortable for some close triads, but it is not part of the chord's definition. Adjust fingering around black keys while keeping the wrist neutral and all three pitches correct.

Exercise

Six-chord workshop

For C, Cm, F, Fm, G, and Gm, write root–third–fifth letters first, add accidentals second, and check intervals from the root. The exact spellings are C–E–G; C–E♭–G; F–A–C; F–A♭–C; G–B–D; G–B♭–D.

Play each measure twice: roll low to high to hear the two stacked thirds, then block all notes together. After each major/minor pair, name the changed pitch. Finally, cover the score and rebuild all six from their symbols before checking spelling and quality.

Common mistakes

• Symptom: Building a triad from three evenly spaced keys. Correction: Write alternating root–third–fifth letters first; the two third layers have different keyboard widths.
• Symptom: Spelling Fm as F–G♯–C. Correction: The middle note must be an A because it is the third; lower A to A♭.
• Symptom: Treating a symbol as one fixed hand shape. Correction: Preserve spelling and quality while choosing a playable fingering and voicing.

Frequently asked questions

Is the fifth what makes a triad major or minor? No. Both qualities here use P5. The third is major in a major triad and minor in a minor triad.

Can I omit a note and still call it the same triad? Some performance styles omit tones, but this construction exercise requires all three so the spelling and quality remain visible.

Why avoid G♯ in F minor if it is the same piano key as A♭? The chord needs an A-named third above F. A♭ communicates that structure; G♯ does not.