midicnTheory 中文
TriadMajor TriadNatural Minor ScaleHarmonic Function

A minor triad is the mirror image of a major triad: a minor third below, a major third above.

C–E♭–G: C to E♭ is a minor third (3 semitones), E♭ to G is a major third (4)

Compared with a major triad, the root and fifth are identical (still a perfect fifth) and only the third is a semitone lower. Yet it sounds completely different: less stable, darker, and carrying an implication of returning to major — raise the third a semitone and you are back. That one-step-away quality is where its tension lives.

Where it appears

ContextPositions
major scaledegrees 2, 3 and 6 (ii / iii / vi) are all minor triads
natural minordegrees 1, 4 and 5 (i / iv / v) — the tonic itself is a minor triad
minor-key writingdegree 1 as the centre of the piece, degree 4 as subdominant

Note the first row: a major scale also contains three minor triads, the very same number as its major triads. So "major key means major chords" is wrong — three major, three minor and one diminished triad make up the complete set of seven, as covered under scales as harmony.

Its relation to minor keys

In natural minor the seventh degree is unraised, so the chord on degree 5 (the dominant) is a minor triad and its push to the tonic is weak. That is precisely why minor-key music almost always raises the seventh (see harmonic minor) — the point is to turn the dominant back into a major triad.

Diagram: the mirror relation

Swap the two thirds and the quality flips from major to minor CEG CE♭G major third + minor third = major triad minor third + major third = minor triad Shared: root to fifth is a perfect fifth (7 semitones) — the same frame Different: the third sits a semitone lower — and that splits dark from bright

Listen: the minor triad

Hear it as a block first (dark, inward), then press Arpeggio to hear the third sitting a semitone below the major version.

Common misconceptions

Listen in the library

Scales, Arpeggios, and CadencesC13:22Minor-triad arpeggios in scale exercises, directly comparable with the major-triad onesDetails27. Greensleeves to a Ground with DivisionC10:24Greensleeves moves in small intervals and steps, and its harmonic base is the minor triadDetailsSonata in A Minor, K.175C13:50A sonata in A minor — its tonic is a minor triad, and the whole piece is centred on itDetails

All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).

Sources

  • 小三和弦 = 小三度 + 大三度，根音到五音仍为纯五度，属和声学通则
  • 小三和弦与大三和弦共用同一骨架、仅三音高度不同，为通行和声学表述

Used for fact-checking only; all prose is original.