How Chords Are Built

Begin with how chords are built

Chord construction combines written scale degrees with measured semitone distances. Both are needed for correct spelling.

This guide builds the subject in a sequence: orient the written symbols, connect them to keyboard distance, compare related structures and finish with tasks that can be checked from the visible answer. The aim is a reusable reference, not a claim that reading one page guarantees a learning outcome.

Vocabulary and visual landmarks

A tonic or root is the named reference note. A scale degree describes position relative to a tonic; an interval combines a numbered letter span with a quality; a chord formula selects several of those degrees. On the keyboard, groups of two and three black keys provide position landmarks but do not decide theoretical spelling.

The original diagram pairs highlighted keys with a text line. Read both: the shape makes spacing visible, while the note names preserve accidentals and diatonic function.

Build the answer step by step

First state the root or tonic. Next apply the interval or degree formula. Then assign the required letter names before adding accidentals. Finally compare each resulting pitch with the keyboard. Reversing that process—choosing the nearest key label first—can produce plausible sound with incorrect notation.

Use A minor chord is 1–♭3–5: from A, those letters are A, C and E. as a worked model. Change one variable at a time so the reason for each new note remains visible.

• Identify the reference note.
• Write the degree or interval formula.
• Advance through the required letter names.
• Apply accidentals to reach the target pitches.
• Check the keyboard and text answer together.

Symbols, extensions and exceptions

Chord and scale shorthand compresses several decisions. A chord symbol may include a root, quality, added or extended degree, alteration, omission and bass. A scale name may imply a seven-note parent, a five-note degree selection or a directional convention.

Pentatonic scales therefore use explicit parent-degree maps rather than consecutive stored letters. Chromatic displays are labelled ascending-sharps and descending-flats conventions instead of claiming one context-free spelling. Classical melodic minor distinguishes ascent from the common natural-minor descent.

Worked comparisons

Compare C major, C minor and C suspended-fourth while holding the root and fifth constant. Compare C major, A natural minor and C natural minor to separate relative from parallel relationships. Compare C–F♯ with C–G♭ to hear the same equal-temperament distance while reading two different interval names.

Each comparison isolates one theoretical decision. The diagrams are generated from first-party data and use no copied notation or copyrighted repertoire.

Common errors to catch

Counting piano keys alone can find pitches but can miss the correct written interval name.

Other warning signs include repeated letter names inside a seven-note diatonic scale, skipped letters in a triad, extreme accidentals in ordinary practical keys, or a pitch-class match presented as one definitive chord despite missing tones.

Intervals are the raw material

A chord formula names distances above a root. The major triad uses a major third and perfect fifth; the minor triad changes the third to minor; diminished lowers both third and fifth relative to major; augmented raises the fifth. Semitone counts confirm sound, while letter counts preserve the written interval names.

From D, a major third must be some form of F and land four semitones above D, giving F♯. A perfect fifth must be some form of A and land seven semitones above D, giving A. This two-part test is more reliable than selecting the closest familiar key name.

Stacking thirds to make triads

Diatonic triads can be found by selecting alternate notes of a scale: take degree 1, skip 2, take 3, skip 4 and take 5. In C major this yields C–E–G on I, D–F–A on ii and B–D–F on vii°. The letters visibly form stacked thirds even though the semitone qualities vary.

Building from a scale explains why triad quality changes by degree. Building from an interval formula explains how to transpose that quality outside a single scale. ChordMetric uses both views and requires their outputs to agree.

The four basic triad qualities

Major is 1–3–5; minor is 1–♭3–5; diminished is 1–♭3–♭5; augmented is 1–3–♯5. With C fixed, these become C–E–G, C–E♭–G, C–E♭–G♭ and C–E–G♯. Each step changes one degree from an adjacent comparison.

Do not describe diminished as “minor with a different black key” or augmented as “major moved outward”. The degree names matter: a diminished fifth and augmented fifth retain fifth-letter spelling even when an enharmonic keyboard label looks simpler.

Suspended and power structures

A suspended chord replaces the third. Csus2 is C–D–G and Csus4 is C–F–G; without E or E♭, neither structure states major or minor quality by itself. A C5 power structure similarly contains C and G without a third, though doubling and octave placement are common in practice.

Historical voice-leading can explain the word suspended, but a modern chord symbol does not guarantee that the suspended tone will resolve. Chord identity describes the present pitch roles; progression and voice-leading describe what surrounds them.

Sixths and added notes

C6 adds A to C–E–G, giving 1–3–5–6. Cm6 changes the third but retains the major sixth: C–E♭–G–A. Cadd9 adds D above the triad without requiring a seventh. These labels state direct additions rather than a complete tertian extension stack.

An added ninth and added second can share pitch class while implying a different registral description. Chord identity need not dictate exact octave, so the visible voicing may place the added tone near the triad while the symbol preserves its degree name.

Seventh-chord construction

Continue the stack of thirds by adding a seventh. Cmaj7 is C–E–G–B; C7 is C–E–G–B♭; Cm7 is C–E♭–G–B♭; Cdim7 is C–E♭–G♭–B𝄫; and Cø7, or Cm7♭5, is C–E♭–G♭–B♭. Each quality is a specific combination, not merely “a triad plus any seventh”.

The fully diminished seventh illustrates why double accidentals can be correct in theoretical structures even though the practical-key guard rejects extreme accidentals from ordinary scale pages. B𝄫 is a diminished seventh above C; A is the same piano key but describes a sixth letter.

Ninths and other extensions

Ninth, eleventh and thirteenth chords continue the theoretical third stack. A dominant ninth uses 1–3–5–♭7–9. A major ninth uses 1–3–5–7–9. Longer symbols may alter individual extensions, such as ♭9 or ♯11, while retaining the underlying seventh quality.

Practical piano voicings may omit the fifth, double the root or distribute tones between hands. Those choices manage texture and range; they do not rewrite the complete theoretical formula shown by the reference.

Inversion versus voicing

Inversion is determined by the bass chord tone. C–E–G is root position, E–G–C first inversion and G–C–E second inversion. A seventh chord adds a third inversion with its seventh in the bass. Rotating ordered notes provides a clear close-position comparison.

Voicing describes spacing, doubling and register. C3–G3–E4 and C3–E4–G4 are both root-position C-major voicings. E3–C4–G4 remains first inversion because E is lowest even though the upper tones are spread.

Chords derived from scales

Stacking alternate degrees of a major scale produces major, minor, minor, major, major, minor and diminished triads. Natural minor produces minor, diminished, major, minor, minor, major and major triads. Harmonic practice may raise scale degrees and therefore introduce other chord qualities.

Roman numerals separate these functions from absolute note names. Uppercase identifies major-type triads, lowercase minor, and the diminished symbol marks a diminished fifth. The key must remain visible because the same letter-named chord can take a different function elsewhere.