Chords in a Key
One scale, and everything that fits inside it — the chord on every degree, the sevenths, the pentatonics, on your instrument.
A key is not a list of chords you look up. It is one scale — seven notes out of twelve — and everything that fits inside those seven: the chord you can build on each of them, the seventh chord on each, the pentatonic scale on most of them. Learn a key as a set of notes and the chords come for free, because a chord in the key is just some of the key's notes sounded together.
Above is C major on the guitar: the seven notes across the whole neck, and over the neck a row of chips, one for the chord on each degree. Tap a chip to lift that chord out of the scale — its notes stay full size, the rest of the scale shrinks around them, the chord's root gets the ring. The dropdown switches the row to seventh chords or pentatonics; the shape menu draws the chord as one voicing at a time, ‹ › through them; the picker changes the instrument, the capsule the key. The link under the figure is the page for whichever key you set — every major and minor key on every instrument has one. From here on the figure follows the text.
One scale, seven notes
C major is C D E F G A B. Every note on the neck that is one of those seven is drawn; every note that is not is left out. That is the key — nothing more. The notes are labeled by degree, 1 to 7 from the root, in the app's degree colors: the same picture in every key, only the fret numbers change. The major and minor scale is the page for the scale itself.
The chord on every degree
Each degree's chord, stackedTake any note of the scale, skip one, take the next, skip one, take the next: three notes of the key a third apart, a triad. Do it on every degree and you have the six chords everyone means by "the chords in C": C, Dm, Em, F, G, Am — three major, three minor, and B diminished on the seventh degree, which the explorer leaves out as a chord nobody rests on. Tap a chip and look at the neck: the chord is those three degrees, everywhere they occur, and the rest of the key is still there behind them, small. That is the whole idea of the figure: a chord is not a grip, it is a subset of the key.
Roman numerals
The chips carry numerals — I ii iii IV V vi — because the chord on a degree is the same job in every key, and the numeral names the job: I is home, IV and V sit a fifth either side of it and between them hold every note of the scale, ii iii and vi are their minor shadows a third below. Upper case is a major chord, lower case minor, a ° a diminished one — and that string of cases, upper lower lower upper upper lower, is the fingerprint of a major key. Set the capsule to G major and the letters change while the numerals and the colors stay; that is why a chart written in numerals is a song in any key, and why the Nashville system writes the same thing as 1 4 5, 2m 3m 6m. A seventh chord's numeral carries its quality after the number — Imaj7, V7 — and a minor key is numbered from its own root: i, III, iv, v, VI, VII.
Four notes: the seventh chords
Keep stacking — one more third — and each triad becomes a seventh chord, still all from the key's notes: Cmaj7, Dm7, Em7, Fmaj7, G7, Am7. Two major sevenths, three minor sevenths and exactly one dominant seventh, on the fifth degree — which is why G7 sounds like "go home to C", and why a ii–V–I is three chords of this row. The shells are the grips it is played with.
Five notes: the pentatonics
A key also holds scales smaller than itself. Five notes of the seven make a pentatonic, and the row on "Pentatonics" shows six of them inside C major: a major pentatonic on C, F and G, a minor pentatonic on D, E and A — A minor pentatonic being the one guitarists play over the whole key. Major where the degree's chord is major, minor where it is minor; none on B.
A chord as a shape
A chord across the whole neck is a map; a chord you play is one place on it. Set the shape menu to "Basic shapes" and the explorer draws one voicing of C, the halo on its notes, an outline joining them, the key still small behind — ‹ › walks the voicings up the neck. Tap any note on the neck and the explorer finds the chords of the key that hold it, shape by shape: a G is in G, in Em and in C, and the tap walks them. "Inversions" gives the close-position triads, "Useful" the spread ones; every chord of a key has a grip in one position, and stepping through the row keeps the hand where it is.
The same seven notes, another home
A minor is the same seven notes as C major with A as the root: the same six chords, renumbered — Am is i now, C is III, the chips recolored from A — and a minor v where the major key had its major V. Every major key has a relative minor like this, and five other homes besides, the modes: D dorian's row is C major's chords from the second chair, with the major IV that names it. Why the major modes builds the chords of every mode on the wheel and says why these seven.
Every key, on every instrument
Every major and minor key has a page of its own, with the figure opened on it and its chords, seventh chords and pentatonics listed — the reference entry for "the chords in A minor on ukulele" — and the link under the figure goes to whichever key you have set.
The modes' keys, on the guitar:
Questions
- What is a key in music?
- A key is one scale — seven notes out of twelve — and everything built from those notes: the chord on each degree, the seventh chord on each, the pentatonic scales inside it. A song in C major uses the notes of the C major scale and, mostly, the chords stacked from them.
- What chords are in a key?
- The chord on every degree of the scale, stacked in thirds from the key's own notes. In a major key that gives I ii iii IV V vi — three major, three minor — and a diminished chord on the seventh degree; in C major, C Dm Em F G Am.
- Are the chords in a minor key different?
- They are the same chords as its relative major, renumbered from the minor root: in A minor, Am C Dm Em F G, i III iv v VI VII. The v is minor; the major V most minor songs use is borrowed from the harmonic minor scale.
- Which pentatonic scale goes with a key?
- A major key holds three major pentatonics, on its I, IV and V, and three minor ones, on its ii, iii and vi. The major pentatonic on the root and the minor pentatonic on the relative minor are the same five notes and fit every chord in the key.