Anatomy of a Chord

F♯ is F♯, A♯, C♯. Bright and settled. The major 3rd is what makes it sound open.

1. The notes

The most concrete description of a chord is the list of notes in it. F♯ major is F♯, A♯, C♯. Three notes, three keys you press, done. No Roman numerals, no arithmetic, just letter names.

What looks arbitrary at first, why A♯ and not B♭, is a deliberate spelling choice. A triad uses every other letter going up: F, then A, then C, skipping G and B. Spelling that middle note B♭ instead of A♯ gives you exactly the same key on the piano, but on the page F♯ up to B♭ reads as a fourth rather than a third, and the chord stops looking like a triad at all. The accidental follows from the letter, and the letter follows from the chord.

When notes are most useful: sight-reading, looking up a fingering, or playing a chord you have never seen. Notes tell you exactly which keys to press, right now.

2. The intervals

An interval is the distance between two notes. Every chord can be described as a set of intervals measured up from the root.

A major triad has a major 3rd and a perfect 5th above its root, so its interval list is P1, M3, P5. A minor triad swaps the major 3rd for a minor 3rd: P1, m3, P5. That one half step in the middle is the whole difference between the two most common chords in music.

Interval names have two parts. The number counts letter names inclusively, so C up to E is a third because C, D, E is three letters. The quality word fixes the exact size: perfect (unisons, 4ths, 5ths, octaves), major and minor (2nds, 3rds, 6ths, 7ths, a half step apart), diminished (a half step below perfect or minor) and augmented (a half step above perfect or major).

When intervals are most useful: working out why a chord sounds the way it does, or moving it to another key. Intervals are key-independent. A major 3rd is a major 3rd whether the root is C or F♯.

3. The formula

The formula is the most compact description. It uses degree numbers from the major scale of the root, with sharps and flats marking where a note has been raised or lowered.

Major triad: 1-3-5. Take the 1st, 3rd and 5th notes of the major scale of your root. For C that is C, E, G. For F♯ it is F♯, A♯, C♯. Same recipe, different ingredients.

Minor triad: 1-♭3-5. Same three degrees, but lower the 3rd by a half step. C major’s 3rd is E; lower it to E♭ and you have C minor.

Why it is built on the major scale: convention, and a useful one. The major scale is the shared reference grid, so 1-3-5-♭7 means the same thing on every root: take 1, 3 and 5 from that root’s major scale, then flatten the 7th. Learn the major scales and every formula resolves without thinking.

When the formula is most useful: learning a new chord type, transposing on the fly, or comparing two chords side by side. The formula is what makes the family resemblance visible. Major and minor differ by one symbol; dominant 7th and major 7th differ by one symbol.

4. The scale degrees

Scale degrees describe a chord’s position inside a parent key. They answer a different question: if we are in C major, what is this chord doing?

Every major scale carries seven triads, one on each degree, all built only from notes of that scale. In C major: C is the I chord, D minor is ii, E minor is iii, F is IV, G is V, A minor is vi, and B diminished is vii°. The numeral gives the degree, and the case gives the quality.

Formula against scale degrees, the subtle difference: the formula describes a chord on its own, always relative to the major scale of that chord’s root. Scale degrees describe the chord’s role inside a key. F major’s formula is always 1-3-5, but in C major F is the IV chord and in F major it is the I chord. Same notes, different job.

All four together: F♯ major

Every chord page on this site stacks the same four pieces of information in its header. Here is what each line is telling you.

None of the four is more correct than the others. They are different tools. Notes are best for sight-reading, intervals for analysis, formulas for memorising chord types, scale degrees for understanding harmony in context. Fluent musicians switch between them without noticing.

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