Triads and inversions: quick construction and recognition

Definition

A triad is a chord of three notes stacked in thirds: root, third and fifth. There are four qualities:

To these are added, outside stacking in thirds, the suspended chords (Csus2 C D G, Csus4 C F G) and the power chord C5 (C G), covered in other cards.

Method for building them in any key

1. Letters: take the root and skip a letter twice: F → A → C; B → D → F; Eb → G → B.
2. Quality: adjust the accidentals to get the desired intervals. Start from the “white-key” triad and compare:

• Natural major triads: C, F, G. Minor: Dm, Em, Am. Diminished: B°.
• To build Eb major: E G B → lower everything by a semitone → Eb G Bb.
• To build F# minor: F A C → raise everything → F# A# C# (F# major) → lower the third → F# A C#.

1. Check: a triad must be spelled with three alternate letters. G# B# D# (G# major) is correct; G# C D# is not.

Inversions

The inversion depends only on which note is in the bass, not on the order of the upper voices.

The numbers indicate the intervals above the bass: in first inversion, above E there are a 3rd (G) and a 6th (C).

How to recognize an inversion on the score or in the Piano roll

• Reduce the notes to close position and look for the arrangement in thirds: the lowest note of that stack is the root.
• If there is a fourth between two notes, the upper note of the fourth is the root (G–C → C).
• If there is a sixth between two notes, the upper note is often the root (E–C in first inversion).
• Then look at the actual bass: if it is the root = root position; if it is the third = first inversion; if it is the fifth = second inversion.

Close position, open position and doublings

• Close position: the three upper voices lie within an octave. Open position: the voices are spread apart (more than an octave between soprano and tenor).
• Four-voice doublings (common practice): in root position double the root; in first inversion the soprano or the root is often doubled, and doubling the leading tone should be avoided; in second inversion double the bass (the fifth).
• Sound quality: root position is stable, first inversion is lighter and “in motion” (great for descending bass lines), second inversion is unstable and is used in specific ways (cadential 6/4, passing, neighbor, arpeggiated).

Examples in real songs

• “A Whiter Shade of Pale” (Procol Harum): the bass descends by step (C – B – A – G – F – E – D…) under chords that alternate root positions, inversions and passing bass (C, C/B, Am, Am/G, F, F/E, Dm…): a manual of bass-line writing.
• “Let It Be” (The Beatles): in the verse G/B appears between C and Am, a first inversion that makes the bass descend C–B–A.
• Pachelbel, Canon in D: modern realizations often use first inversions (D, A/C#, Bm, F#m/A…) for a bass moving by step.

Inversions in production

• In pads and piano voicings move the voices as little as possible (voice leading): C–Am–F–G played as C(E G C)–Am(E A C)–F(F A C)–G(D G B) is smoother than always in root position.
• Leave the bass (synth bass, 808) on the root and use inversions only in the upper parts: you get movement without confusing the harmony.
• A first-inversion bass (C/E) adds lightness in pre-choruses; a second-inversion bass (C/G) is an excellent suspension chord before the dominant.

Exercise

1. Build the four triad qualities on F#, Bb, Db, G#: write the notes and check the letters.
2. Play I–vi–IV–V in C with all chords in root position, then with the upper voices as close together as possible: compare on a pad.
3. Write a descending bass C–B–A–G–F–E–D–G using only diatonic triads and their inversions.

Related topics

Triads: qualities and diatonic chords; Chord inversions and six-four chords; Inversion figures in analysis; Voice-leading rules.