Chords

Press one key and hold it. A note sounds, and that is all: no mood, no motion, just a pitch. Now press three white keys together, skipping one each time: C, E and G. That is already music. It is the last chord of a song, the opening of an anthem, the first bar of a thousand tracks.

This chapter builds an instrument that does that trick with a single key. Call it the smart key: you press one note and it plays a chord. At first it has one setting, by the end of the chapter five, and you will know what each of them does and why.

One key, three notes

Here is the smart key at its simplest. The "A key plays" switch is set to "one note". Walk up the white keys from C to C. Then switch it to "a chord" and walk up again.

With chords, every key sounds complete. The smart key does what your hand did a moment ago: it takes the note you pressed and adds two white keys above it, skipping one each time. C gives C–E–G, D gives D–F–A, E gives E–G–B. The labels above the keys show what you will get: C, Dm, Em, F, G, Am, Bdim. You met these letters in chapter 5, and we will come back to them.

Listen to how the chords differ. C, F and G sound bright, D, E and A darker, and B sounds cramped and uneasy. They are all built the same way, one white key apart, yet each has its own character. Where the difference comes from will be clear in the next section.

Three or more notes of different pitch played together make a chord. A three-note chord built the way you just did, skipping a degree each time, is a triad. For now the smart key skips the black keys: they are not in C major, and it builds its chords from the notes of C major.

A chord of thirds

The step "skip one white key" is a third. In chapter 13 you met two thirds: an interval of three semitones is a minor third (m3), of four a major third (M3). A triad is two thirds stacked one on top of the other, like the floors of a tower.

The floors have names. The bottom note, the one the chord is built from, is the root. The middle note sits a third higher and is simply called the third. The top one is the fifth, because it lies a fifth above the root. Build the tower yourself: choose a root and the size of each third.

Start on C: M3 below, m3 on top, and you get C–E–G. Now switch the lower third to m3. One note moves, E becomes E♭, and the bright chord turns dark. Put M3 back and press any key on the widget's keyboard: it becomes the root, and the tower rebuilds from it. The pattern "M3, then m3" sounds equally bright from any note, even though it looks different on the keys: on D the middle note is the black F♯, on D♭ the two outer notes are black.

The middle floor decides whether the chord is bright or dark, just as the third degree decided whether a scale was major or minor in chapter 14. The fifth on top stays put and holds the chord together like a roof: it is seven semitones above the root, however those semitones are split between the two thirds.

A triad sounds, all three notes together. Decide whether the major or the minor third is at the bottom.

Four kinds of triad

There are two thirds, and each can be minor or major. So there are exactly four kinds of triad. No other combinations exist.

Lower	Upper	Outer notes	Triad	On C
M3	m3	P5, 7 semitones	major	C–E–G, C
m3	M3	P5, 7 semitones	minor	C–E♭–G, Cm
m3	m3	d5, 6 semitones	diminished	C–E♭–G♭, Cdim
M3	M3	A5, 8 semitones	augmented	C–E–G♯, Caug

The major triad and the minor triad are mirror twins: the same two thirds in reverse order, with the same fifth across the outside. Nearly all the music you hear every day rests on these two. The other two combinations are rare guests. The diminished triad is squeezed: its outer fifth is a semitone narrower than usual, the tritone from chapter 13. The augmented triad is the opposite, stretched by a semitone, and sounds unsettled, as if the chord had forgotten where it was going.

Back to the smart key: it now has a second setting, "Chord quality". Leave it on "from the key" first and look at the labels. The white keys give three major triads (C, F, G), three minor (Dm, Em, Am) and one diminished (Bdim). The thirds between white keys are sometimes minor and sometimes major, and which you get depends on the key you start from. There is no augmented triad at all: C major never has two major thirds in a row.

Now choose "major". The key has stopped looking at the scale: from any note, white or black, it builds the same shape, M3 + m3. D no longer gives Dm but D, with F♯ in the middle, and the black keys have joined in. This is how the simple chord modes on synths work: one shape, moved around the keyboard. Switch to "dim." and "aug." and walk across the keys. The diminished chords pull somewhere, the augmented ones seem to hang in the air.

Tell major from minor by the middle note, and the rare guests by the outer ones: diminished is tight and pulls, augmented spreads and blurs.

What kind of triad is B–D–F?

Diminished: both thirds are minor Minor: there is a minor third at the bottom Major: all the notes are white

From B to D is three semitones, and from D to F three more: two minor thirds. In a minor triad only the lower third is minor, the upper one is major, and the outer notes make a perfect fifth, 7 semitones. Here, from B to F is six semitones, a tritone. White keys tell you nothing about the kind: the white keys have every kind except augmented.

Letters above the line

In chapter 5 you saw chord symbols, and now you can read them in full. The letter is the root. If nothing follows it, the triad is major. A small m means minor, dim diminished, aug augmented (sometimes written ° and +). A sign after the letter belongs to the root: F♯m is F sharp minor, B♭ is B flat major. The figure 7 adds a fourth note, which comes later.

In German and old Soviet songbooks you may meet one more letter: H. It is simply B, in the German tradition. Chapter 5 tells how that came about (H and B). H7 in such a songbook is the same as B7 in an American one.

Reading a symbol and playing the chord is half the job. The other half runs the other way: you hear three notes, or see them under your fingers, and work out which chord it is. Hold any notes together and the widget names the chord: its letter, its kind and which note is in the bass.

Try A, C and E: Am. Now let go of E and look at the highlighted keys. These are the notes that would turn the pair back into a triad. There are several, because two notes can belong to different chords: A and C appear both in Am and in F. Now play C–E–A: the same notes, with A moved to the top. The widget names the same Am and adds "/C": the slash means "with C in the bass". Songbooks write it this way when it matters which note of the chord sounds at the bottom.

On the staff a triad is easy to spot. Three notes a skip apart sit either on three neighbouring lines or in three neighbouring spaces, a shape musicians call a snowman. Here are all the triads of C major in order: watch the snowman climb while the kind of chord changes by itself.

Triads on the white keys: a snowman on every degree

The exercise shows a chord symbol. Play all three notes together, in any order. Take your time: find the root first, then count up two thirds.

Inversions: the hand barely moves

Play C, F, G and C again in a row, each chord from its root. Your hand jumps: C–E–G, then the whole hand up to F–A–C, then higher still to G–B–D and back down. In a slow song you can live with it. In a fast one you will not make it in time, and each chord sounds separate, as if there were a gap between them. Experienced keyboard players do not play like that. Switch the widget between the two ways and compare.

In "nearest position" the lines between the chords are almost flat, and the green ones do not move at all. These are common notes: C and F share C, G and C share G, and there is no reason to let go of them. The other fingers shift by a semitone or a tone. For C–F–G–C the fingers travel 12 semitones in total over one round instead of 42, and no finger jumps more than three semitones.

Where is the trick? The F chord is still F–A–C, only the C has moved down: C–F–A. Same notes, different order. A rearrangement like this is an inversion of the chord. When the root is at the bottom, the chord is in root position. With the third at the bottom it is in first inversion: E–G–C. With the fifth at the bottom, second inversion: G–C–E.

Inversions also have older names, taken from the intervals above the bottom note. In E–G–C there is a sixth from E up to the top C, so first inversion is called a sixth chord, written 6 in figured bass. In G–C–E there is a fourth (C) and a sixth (E) above the bottom G: a six-four chord, written 6-4. In English you will mostly hear just "first" and "second inversion". These are Rameau's chords from the story above: they sound a little different, but the ear hears the same C in all of them.

The way each note of a chord moves to a note of the next one is called voice leading. The rule of nearest position is simple: hold the common notes, and move the rest to the nearest note of the new chord. The smart key can now do this by itself, with the "Position" setting.

Play C, F, G, C with one finger. Under the label you can see which inversion the key chose and how many semitones the fingers moved. Switch to "up from the key" and do it again: the same chords, and the hand is jumping once more. You can hear the difference too: nearest position joins the chords into one line, while root position chops them into pieces.

Now the chords come in any inversion. The middle note is no longer always the third, so listen to the colour of the whole chord.

Now with your hands. This exercise has four chords in a loop, and you can play them in any inversion. Try the nearest: C as C–E–G, G as B–D–G, Am as C–E–A, F as C–F–A. Your thumb hardly leaves C.

The fourth floor: the seventh chord

You can put a third third on top of the tower of two. Then the top note is a seventh above the root, and the four-note chord is called a seventh chord. Add a floor in the builder.

The most important of them is a major triad with a minor seventh on top: G–B–D–F. In chord symbols it is written simply with the figure: G7. It lives on the fifth degree of the scale, so it is usually called the dominant seventh. Where "dominant" comes from is in the next section. Two of its notes want to resolve at once: B pulls up to C, and F down to E. Listen: G7, and then C. A question and an answer.

Other seventh chords sound softer. Cmaj7 is C–E–G–B, major with a major seventh, the dreamy chord of jazz and lounge. Am7 is A–C–E–G, minor with a minor seventh, warm and unhurried. Mind the spelling: in Cmaj7 the "maj" refers to the seventh, not the triad, and without it a 7 always means a minor seventh.

Switch the smart key to four notes and walk up the white keys. The labels have changed: Cmaj7, Dm7, Em7, Fmaj7, G7, Am7 and Bm7♭5. Each degree has its own seventh chord, and there is only one dominant seventh among them, on G.

Major, minor, or a seventh chord like G7? The seventh sounds like an extra, slightly prickly note on top that asks to go on.

I, IV, V: the three primary chords

The smart key builds its "from the key" chords on the degrees of the key. It is handy to name them by degree rather than by letter, because then one label fits any key. These are roman numerals: an upper-case numeral is a major triad, lower-case a minor one, and a small circle diminished. In C major they are I (C), ii (Dm), iii (Em), IV (F), V (G), vi (Am) and vii° (Bdim). In G major the numerals are the same and the letters different: I is G, IV is C, V is D.

Three of the seven chords matter more than the rest: I, IV and V, all three major. These are the primary triads. Add up their notes: C–E–G, F–A–C, G–B–D. Together that is C, D, E, F, G, A, B, all seven notes of the scale and nothing extra. So for any note of a tune in C major there is a primary chord that contains it, and that is why so many songs get by on three chords.

The primary chords have names. The tonic triad is built on the tonic, and it is home. Degree V is the dominant, from the Latin dominans, "ruling": after the tonic it is the strongest anchor of the key. Its chord contains the leading note, B, which pulls towards C, and that is why V wants so badly to move to I. Degree IV is the subdominant, the "lower dominant". The name is honest: a fifth up from C is G, a fifth down from C is F. The tonic stands in the middle, with a dominant on either side.

German and Russian textbooks often label the primary chords with the letters T, S and D, for tonic, subdominant and dominant. That notation goes back to the German theorist Hugo Riemann and his "Simplified Harmony" of 1893. This course writes I, IV and V, the way English-language textbooks, the chord tools in DAWs and most song analyses online do. The "Chord functions" trainer knows both.

The smart key's last setting is the key. Choose a tonic and a mode, and the labels above the keys change to show which chord each degree gives in that particular key. The numerals above the letters stay the same.

Try G major: with one finger play G, C, D. That is I, IV, V, and vii° has appeared over F♯. Then A minor: Am, Dm, Em, that is i, iv and v, all three minor. In minor the pull towards the tonic is weaker: in natural minor the seventh degree is a whole tone below the tonic, so there is no leading note. That is why for centuries composers have raised the seventh degree in minor, as in the harmonic minor of chapter 14, and v becomes a major V: E instead of Em in A minor. Play Am–Dm–Em–Am, and then Am–Dm–E–Am. The second ending sounds firmer.

By ear you tell I, IV and V apart by their pull. The exercise first plays I–IV–V–I, so your ear knows where home is, and then one chord. I sounds settled. V is like a question that makes you want I. IV is a gentle step away from home, without such a strong pull.

Now a bet. The widget plays a short phrase with its last chord hidden. What will it end on? Choose, listen to your ending, and then to the others.

All four phrases end on V, and most people bet on I. That is not a textbook rule but an expectation the ear has learnt from thousands of songs: after the dominant comes the tonic. Composers use it both ways. They give you I when they want a full stop, and trick you with vi when the song has to go on. Other ways to answer V are the subject of chapter 19.

The same primary chords in another key: G, C, D and the dominant seventh D7. D and D7 have a black key, F♯.

The shortest way out of home and back. After C–F–A, play G7 as B–D–F–G: F stays where it is, C steps down to B, A to G, and one more finger adds D. The exercise waits for all four notes.

Which chord is V in F major?

C: C–E–G B♭: B♭–D–F G: G–B–D

The degrees of F major are F, G, A, B♭, C, D, E. The fifth is C, so V is the C major triad, C. B♭ is IV, a fifth below the tonic. G stands on degree II, and in F major it would be minor, Gm, with B♭ instead of B.

Three trainers help you keep the primary chords in your hands and ears: "Chords by ear", from major and minor up to seventh chords, "Playing chords", a symbol on the screen and the chord under your fingers, and "Chord functions", I, IV, V and beyond.

One finger, a whole band

The smart key is not an invention of this chapter. Instruments that play a chord from a single button have been around for almost two hundred years, and in the 1980s they stood in a great many homes where someone wanted to learn music.

Here is such a keyboard. The accompaniment zone is lit on the left, and the keys for the tune are on the right. Press C in the zone and C plays. Add any key to its right for Cm, and one more for C7. Casio Chord works this way on the models made today, too, and four keys also give a minor seventh chord. Switch on the rhythm and play C, F, G, C with one finger, and something simple on top with your right hand.

Notice what auto-accompaniment can do and what it cannot. It knows perfectly well how to play a chord: in which inversion, with what bass, in what rhythm. But it has no idea which chord is needed right now. That is your decision, and that is what all the previous sections were for: the kind of chord, the symbols, the degrees, the pull of V towards I.

The chord track

Time to give your track some chords. The widget takes the tune and the key from the Notebook. Each bar gets one chord: choose a bar and press a key of the scale, and the smart key puts the chord of that degree there. The labels above the keys are roman numerals, so the key can be any.

Start with the simplest plan: I in the first bar, V in the last but one, I in the last. Listen to it with the tune. If a bar clashes with the tune, try IV or V there: together the primary chords contain every note of the scale, so one of the three will fit. How to choose a chord for the notes of a tune on purpose rather than by guesswork is the subject of chapter 19.

Next

Now you know why three keys a skip apart sound like music: they are two thirds, and their order decides whether the chord is bright or dark. You can tell major, minor, diminished and augmented triads apart by ear, read C, Am, F♯m and G7, move from chord to chord by the nearest path, and find I, IV and V in any key. The smart key is no longer a mystery: you understand each of its settings and can play the same thing without it.

The next wall is tempo. You know what to play, but playing from the page without stopping and without looking at your hands is a skill of its own. That is the job of chapter 16.

The Notebook now has a chord track: one chord per bar, chosen from the degrees of your track's key, and four ways to play them: whole bars, halves, on every beat, or as an arpeggio. In chapter 16 you will play your tune in time over this accompaniment.