Harmony
Chords: Triads and Sevenths
A chord is three or more notes sounded together; stack two thirds and you have a triad, stack a third third and you have a seventh chord, and the symbol printed above the staff is shorthand for which of them to play.
Intermediate · 6 sections
Stacking Thirds
Play the first one. A single note, then a second note joins it, then a third, and nothing ever leaves. Now play the second one, built the same way out of notes that are next-door neighbours instead. One of the two stops sounding like separate notes and starts sounding like one thing. Which one?
| Degree of C major | Note | Taken by the three-note stack? |
|---|---|---|
| 1st | Yes — the note the stack is built up from | |
| 2nd | No — skipped, which is what turns the first gap into a third | |
| 3rd | Yes — a third above the first | |
| 4th | No — skipped | |
| 5th | Yes — a third above the third, and a fifth above the first | |
| 6th | No — skipped | |
| 7th | No — but it is where the stack arrives next if it keeps going |
A chord is three or more notes sounded together, and a triad is a chord of three notes built by stacking thirds: a root, the note a third above it, and the note a third above that.
The two clips are the same size and the same length and they do not sound alike at all. Three neighbours sounded together — C, D and E — stay three separate notes: they are close enough to interfere with one another, and the ear keeps hearing the rub instead of the whole. Skip a note between each pair and the interference goes. C, E and G blend into a single object with a colour, which is why a stack of thirds is the thing harmony is made of and a stack of steps is an effect.
The stack has a bottom, and the bottom has a name. The note the thirds are counted up from is the root, and it is what the chord is named after. It is not necessarily the lowest note being played, and it is not necessarily the note the tune is on — it is the note the stack was built from, which is a fact about how the chord is put together rather than about where it happens to sit.
Thirds are also how a chord gets built out of a scale rather than out of thin air. Take any scale degree, skip the next, take the one after, skip again, take the one after that: every other degree. That procedure run on the seven degrees of a key is where every chord in that key comes from, and it is the whole subject of Chapter 11.
Fact
Stacking thirds is the same operation as taking every other note of a scale. Counting up — C, D, E, F, G, A, B — and keeping the 1st, 3rd and 5th gives ; the two notes left out, D and F, are exactly what make the two remaining gaps Major Third and Minor Third rather than steps.
Convention
Building chords from thirds is a choice Western harmony made, not a law of sound. Stack fourths instead and you get the quartal harmony that McCoy Tyner and a great deal of film music run on; replace the third with a second or a fourth and you get and ; leave the third out altogether and you get the two-note a guitarist plays. All of those are chords. None of them is a triad.
You already know this
Where this goes
In real music
- Twist and Shout, The Beatles — the long rising "aah" before the last verse is one stack of thirds sung a note at a time — one voice, then a third above it, then a third above that — and held until all three are sounding together
See also
Play any note on your instrument, then the note two letters up from it, then two letters up again: C, E, G, or D, F, A, or G, B, D. Do it from four different starting notes, and each time play all three together once you have found them.
Check 1
Three notes, sounded together. Were they built by skipping a note between each one, or are they three neighbours with nothing skipped between them?
The Four Triads
Play all four. Every one of them starts on the same bottom note and every one of them has three notes. Only the middle note and the top note ever move, and never by more than a half step. Two of the four sound settled, as though they could stop there. The other two sound like they are on their way somewhere. Which two are which? The fifth clip plays the four of them straight through, one to a bar, which is the staff below exactly as it is printed.
A triad’s quality is the name it takes from which two thirds it is stacked out of — major, minor, diminished or augmented — and those four are the only possibilities there are.
The arithmetic is short enough to do in your head. Each of the two thirds is either the wide one or the narrow one, so there are four combinations and no more. Wide then narrow is major; narrow then wide is minor; narrow then narrow is diminished; wide then wide is augmented. Nothing else about a triad is free: fix the two thirds and the third note is fixed with them.
The distance between the outer notes follows, and it is what you are really hearing. Major and minor both span Perfect Fifth from bottom to top, which is the most stable distance there is between two different notes, and that shared frame is why both of them can end a piece. The diminished triad spans Diminished Fifth and the augmented Augmented Fifth, both a half step off the stable one, and neither will sit still — the ear takes them as a chord bent out of shape and waits for it to spring back.
So the middle note is what separates major from minor, and the top note is what separates both of those from the two restless ones. That is worth practising as a listening habit rather than a calculation: check the outer frame first, and only then ask about the note in the middle.
Fact
The two thirds settle everything else. There is no further choice to make once they are chosen, and there is no fifth combination: two positions and two sizes give four triads, which is why the list is short and closed rather than a selection from something longer.
Convention
Calling major "happy" and minor "sad" is a description that has hardened into a habit, not a property of the sound. The association is strong in Western listeners and weak or absent in listeners raised on other repertoires, and any number of cheerful pieces are in minor keys. The words in the last column of the table are labels to hang a memory on, and nothing more.
Tendency
Diminished and augmented triads turn up as places a piece passes through rather than places it stays. A phrase can end on a major or a minor triad and sound finished; ending on either of the other two sounds like a question or a cut-off.
Applies to: common-practice classical, jazz and most Western popular music; film scoring and some twentieth-century concert music use both far more freely, and the augmented triad is a stable object in whole-tone writing
You already know this
In real music
- Let It Be, The Beatles — every chord in the verse is a plain three-note one, and the third chord of the first line — the one that lands on the word "trouble" — is the minor among them, which is the whole reason that word sits heavier than the ones around it
- Oh! Darling, The Beatles — the very first chord of the record, struck before anyone sings, is an augmented one: it is why the opening sounds like it is being winched upward rather than simply starting
Play C, E and G together on your instrument. Lower the middle note a half step and play it again. Now lower the top note as well. Put both back where they started and raise the top note instead. Say which of the four you are on each time before you play it.
Build the stack, lower a note, and watch the identifier change its name
Check 1
Three notes together, built up from the same bottom note as the four above. Is the third above that bottom note the wide one or the narrow one?
Check 2
Two of the four triads have an ordinary perfect fifth between their outer notes, and two do not. This is one of the two that do not. Which of them is it?
Inversions
Play the first three. They use the same three notes every time — not one is added, not one taken away. All that changes is which of the three is at the bottom. Does moving the lowest note change what you hear, and if so, how much of it? The fourth clip plays the three of them straight through, one to a bar, which is the staff below exactly as it is printed.
| Position | Lowest note | Notes, bottom to top | What a classical score figures it |
|---|---|---|---|
| Root position | — the root | Nothing at all: no figure under the bass means root position | |
| First inversion | — the third | 6 | |
| Second inversion | — the fifth | 6/4 |
A chord inversion is the same chord standing on a different one of its own notes: take the lowest note, move it up an octave, and the chord keeps its name and every one of its notes while its bass changes. (also called a six chord, or a six-four chord, classical figured bass, where the number under the bass counts the interval up to the root: 6 for first inversion, 6/4 for second; a slash chord, lead sheets and popular music, where C/E means the C triad with E at the bottom)
Nothing is added and nothing is lost, which is why the first three clips are still . The root is still C, because the root is a fact about how the stack was built and not about which note happens to be lowest. A triad has three notes and therefore three positions: root position with the root at the bottom, first inversion with the third at the bottom, second inversion with the fifth at the bottom. A four-note chord has four positions, for the same reason.
The bass note is nonetheless doing most of the work. It is the note the ear uses to locate a chord, so a triad on its third sounds lighter and less final than the same triad on its root, and a triad on its fifth sounds unresolved in a way the other two do not. Inversions are how a composer keeps a bass line walking smoothly while the harmony above it jumps about: the point of an inversion is almost always the bass line, not the chord.
Fact
Inverting changes no note of a chord. All three positions contain C, E and G and nothing else; the only difference is which octave each of them is in, and therefore which of them is lowest.
Convention
The slash spelling names a bass note and nothing more. C/E is the C major triad with E at the bottom, not a C chord played over a separate E chord — and the note after the slash is sometimes not in the chord at all, as in C/D, which is a perfectly ordinary sound and not an inversion of anything.
Tendency
Second inversion is treated as the unstable one: a triad standing on its fifth is usually approached and quit in one of a handful of set ways, most familiarly the chord that lands on the dominant just before a cadence. First inversion, by contrast, is used freely wherever a bass line wants to step rather than leap.
Applies to: common-practice classical voice leading and the counterpoint textbooks that codified it
You already know this
- Inverting an interval in Chapter 5, where the lower note moved up an octave and a fifth became a fourth; a chord is inverted the same way, one note at a time
- The octave from Chapter 2, the distance a note travels when it is taken off the bottom of a stack and put back on the top
- The three-note stack from the start of this chapter, which is what all three of these still are
Where this goes
In real music
- A Whiter Shade of Pale, Procol Harum — the organ line under the whole song walks its bass down one step at a time while the chords above barely change, which it can only do by putting a different note of each chord at the bottom
- Don’t Stop Believin’, Journey — the second chord of the piano intro puts the middle note of a B major chord in the bass, which is why the four-bar figure walks its bass down — E, D sharp, C sharp, A — instead of leaping about
See also
Play C, E and G together on your instrument. Take the C off the bottom and add it back on at the top, then play it again. Do the same with the E. Play all three versions one after another and listen to the lowest note each time rather than the highest.
Put C on top and see the identifier name the inversion
Check 1
F major is spelled F, A, C. Its second inversion puts the fifth of the chord at the bottom. Before you play anything, work out which note that is.
Seventh Chords
Play all five. Each one is a stack you already know from this chapter with one more note added on top, and in three of the five the notes underneath have moved as well. Which of the five sound settled enough to stop on, and which sound as though they are pointing at something that has not arrived yet?
A seventh chord is a four-note chord made by stacking one more third on top of a triad, which lands a seventh above the root and gives the chord its number.
The number counts an interval, not a quantity. A seventh chord has four notes, and the 7 in its name measures the distance from the bottom of the stack to the note that was added — C up to B, or C up to B flat. That is worth saying because the ninths and elevenths in this chapter’s last section are counted exactly the same way, and none of those numbers is a count of notes either.
Two qualities are now in play rather than one: the quality of the triad underneath, and the quality of the seventh on top. Major triad with a major seventh gives ; major triad with a minor seventh gives ; minor triad with a minor seventh gives . Two more come from the diminished triad — with a minor seventh it is , and with a seventh narrowed one half step further it is , whose top note is spelled B double flat because it is still a third above G flat.
The one to learn by ear first is the difference between the first two, because it is a single half step and it changes what the chord wants. is at rest. contains a diminished fifth between its third and its seventh, E against B flat, and that interval pulls: it is why a dominant seventh sounds like an arrow pointing at the chord a fourth above it, and why blues, which sits on these chords without ever resolving them, sounds permanently in motion.
Fact
A dominant seventh contains Diminished Fifth between its third and its seventh — against — and a major seventh chord does not. That one interval is the whole of the difference in how the two behave, and it is why the same four notes crop up again in Chapter 14 as the engine of chromatic harmony.
Convention
A bare number after a letter always means the lowered seventh. is a major triad with a minor seventh on top; the version with a major seventh has to announce itself as . It is the single most common misreading of a chord chart, and it is a convention rather than a logic — nothing about the symbol makes it inevitable.
Tendency
In jazz and R&B the seventh is the default and a bare triad is the marked, deliberately plain choice. In folk, rock, hymnody and most singer-songwriter writing it is the other way round: triads are the ordinary sound and a seventh is added where a chord needs to lean.
Applies to: twentieth- and twenty-first-century Western popular, jazz and folk repertoire
You already know this
Where this goes
In real music
- Something, The Beatles — the first three chords of the verse are the same chord three times with one note walking down inside it — C, then B, then B flat — so the second is a major seventh, the third a dominant seventh, and you can hear the moment the chord starts to lean
- Can’t Buy Me Love, The Beatles — the verse is a twelve-bar blues and every chord in it carries a minor seventh, which is what gives the whole thing its edge instead of a hymn-like squareness
- Autumn Leaves, Joseph Kosma — the second half of the tune turns minor by going through a half-diminished chord and then a dominant seventh, and that pair is the exact moment the song changes colour
Play a three-note stack from any note. Find the note a whole step below the next octave of your starting note and add it on top. Then raise that added note a half step and play it again. Do this from three different starting notes and listen for which version wants to move on.
Add the seventh you chose and read the chord’s name
Check 1
A four-note stack on C. Is the note on top a half step below the octave, or a whole step below it?
Reading Chord Symbols
Play all three. Each one is four notes, and each one is printed under two, three or four different names depending on which book you happened to open. Two of the three differ from one another by a single note. Which two?
- Read a symbol in this order
- the root letter, then any sharp or flat on the root, then the quality, then the number, then anything added in brackets
A chord symbol is the shorthand that names a chord above the staff — a root letter, then a suffix for its quality and any added notes — so that a player can build the chord for themselves instead of reading every note of it. (also called CΔ, jazz lead sheets and hand-copied parts, for the chord this site writes Cmaj7; usually printed CΔ7; Cø, jazz and classical analysis, for the chord this site writes Cm7b5; usually printed Cø7; C-, jazz lead sheets, for the chord this site writes Cm; C°7, classical notation and still the commonest form in print, for the chord this site writes Cdim7)
It is a compressed instruction, and what it compresses is exactly this chapter. The letter gives the root the thirds are stacked from. The quality word or sign gives the two thirds. A number says how far the stack was carried. Everything a symbol can tell you, you can now decode: Cm7♭5 reads as "stack from C, minor triad, add a seventh, and flatten the fifth", which is C, E flat, G flat, B flat.
What the symbol does not say is at least as important. It gives no octave, no order, no doubling and no instruction about which notes to leave out. A pianist playing with the B at the bottom and a guitarist playing it with no fifth at all are both playing it correctly. The symbol names a chord; the voicing is the player’s.
The awkward part is that there is no single standard. Several traditions wrote these symbols down independently — classical figured bass, jazz copyists working at speed, guitar songbook publishers, music software — and each left its habits behind. The table above is not a list of right and wrong spellings but a translation key, and a working musician reads all of them without noticing.
Convention
Chord symbols are conventions, plural, and not a notation system. The same four notes are genuinely, correctly written CΔ7, CM7, Cma7 and Cmaj7, and no authority prefers one. This site writes and because they spell out how the chord is built, which is the more useful form while you are learning; the single-character forms are the more useful once you are sight-reading.
Convention
The circle and the slashed circle are not decoration and are not interchangeable. A plain circle is diminished — as a triad, with a seventh, where the seventh is narrowed too. A slashed circle is half-diminished: a diminished triad with an ordinary minor seventh, . The slash is what tells you only half the chord is diminished.
Tendency
Handwritten jazz parts use the single-character forms — Δ, ø, −, ° — because they are faster to draw and take less width above a melody, while printed pop, guitar and worship books spell the same chords out in letters. If a chart looks like it is using a private code, it is usually just a chart that was written by hand.
Applies to: jazz fake books, hand-copied parts and the Real Book tradition
You already know this
Where this goes
In real music
- The Girl from Ipanema, Antônio Carlos Jobim — the chord under the first sung note is printed FΔ in some fake books and Fmaj7 in others, and it is the same four notes on the page either way
- You Really Got Me, The Kinks — the two-chord riff that opens it has no third in either chord, which is exactly what the 5 in a symbol like F5 is telling a guitarist
Take any chord chart you have — printed, online, or one you remember — and write each symbol out twice: once in the spelling on the page and once in another spelling from the table. Then play four of them on your instrument from the symbol alone, without looking at the notes.
Check 1
A jazz lead sheet has Cø7 printed over the bar. Before you play anything, work out which four notes it is asking for.
Check 2
One of the five seventh chords from this chapter, sounded once on C. Which symbol was printed over it?
Extensions: A First Look
Play all three. Every one of them is a four-note stack from earlier in this chapter with the stacking carried on past the top: one more note skipped and one more note added, and in the third clip that is done twice over. The bottom note has been dropped an octave in all three so that the top of the stack stays clear — nothing else about the four notes underneath has changed. Does the added note arrive as a new event, or as colour on something that was already there?
A chord extension is a note added to a seventh chord by carrying the stack of thirds on past the seventh: the ninth, the eleventh and the thirteenth, which are the second, fourth and sixth degrees of the scale written an octave higher.
Keep stacking and the numbers keep climbing, because they go on counting from the root through the whole stack rather than restarting at the octave. Above the seventh the next third lands on a ninth, the one after that on an eleventh, the one after that on a thirteenth — and then the stack has used all seven notes of the scale and there is nowhere further to go. That is why the list stops at thirteen.
A ninth and a second are the same letter. D above C is a Major Second; the same D an octave higher is a Major Ninth. Nothing about the note has changed. The number is bigger because it is measuring from the bottom of a stack that now has five notes in it, and because calling it a second would suggest it was sitting next to the root, rubbing against it, which is precisely what it is not doing.
In practice these chords are rarely played complete. A symbol like names a six-note chord and a pianist will usually play four of them, keeping the third and the seventh — the two notes that decide what kind of chord it is — and the extension itself, and dropping whatever gets in the way. The symbol is a description of the harmony, not a list of keys to press.
Fact
The numbers count intervals from the root through a continuous stack of thirds, so they run 1, 3, 5, 7, 9, 11, 13 and stop. There is no fifteenth: the next third above a thirteenth is the root again, two octaves up.
Convention
A number in a symbol implies everything beneath it. is understood to contain a seventh, and usually a ninth, even though the symbol names only the thirteenth. The symbol for a ninth without a seventh underneath it is a different one, , and the word "add" is there precisely to say that the stack was skipped rather than completed.
Tendency
The fifth is the first note dropped from an extended chord, and the root is the second, since a bass player is already holding it. A five-note symbol regularly reaches the ear as four notes, and a six-note symbol as four or five.
Applies to: jazz, studio and session piano and guitar voicings
You already know this
Where this goes
In real music
- Just the Two of Us, Grover Washington Jr. and Bill Withers — the two-bar keyboard figure the whole record is built on never plays a plain three-note chord: every chord in the loop carries a seventh and a ninth
- Isn’t She Lovely, Stevie Wonder — the chords under the opening harmonica solo are sevenths with ninths on top throughout, and the ninth is the note that makes them glow rather than merely function
See also
Play a three-note stack from C. Add the note a whole step below the C above it, and play it again. Now add the note a whole step above that C, and play it a third time. Then do all three steps again starting from G instead.
Stack the ninth on top and see what the identifier calls it
Check 1
A C major triad, then the same triad with a seventh added, then the same again with a ninth added. Work out which note arrives last before you play it.
Key Takeaways
- A chord is three or more notes sounded together, and a triad is a chord of three notes built by stacking two thirds on top of one another.
- The two thirds a triad is stacked from decide its quality — major, minor, diminished or augmented — and those four are the only possibilities there are.
- Major and minor triads span a perfect fifth from bottom to top and can end a piece; diminished and augmented triads do not, and generally sound like places a piece is passing through.
- An inversion changes which note of a chord is lowest without changing the chord itself: the same notes, a different bass, and almost always a decision about the bass line.
- A seventh chord is a triad with one more third stacked on top, and the five common ones are the major seventh, the dominant seventh, the minor seventh, the half-diminished and the diminished seventh.
- A bare number in a chord symbol always means the lowered seventh, which is why C7 and Cmaj7 are different chords a single half step apart.
- Chord symbols are several overlapping conventions rather than one standard, so the same four notes are correctly written CΔ7, CM7, Cma7 and Cmaj7 depending on who set the page.
- Extensions carry the same stack of thirds past the seventh to the ninth, eleventh and thirteenth, which are the second, fourth and sixth degrees of the scale an octave higher.
Last updated September 22, 2026
Questions
- What is the difference between a chord and a triad?
- A chord is any three or more notes sounded together. A triad is one particular kind of chord: exactly three notes built by stacking thirds, so that they are the first, third and fifth degrees counted from its own root. Every triad is a chord, and most chords are not triads.
- What does the 7 in C7 mean?
- It means a fourth note has been added a minor seventh above the root — B flat above C — on top of an ordinary C major triad. A bare number in a chord symbol always means the lowered seventh. For the major seventh, B natural, the symbol has to say so: Cmaj7.
- What is a chord inversion?
- It is the same chord standing on a different one of its own notes. Move the lowest note up an octave and nothing is added or removed: C, E, G becomes E, G, C. First inversion stands on the third and second inversion on the fifth, written C/E and C/G on a lead sheet.
- What does Cmaj7 mean, and how is it different from C7?
- Both are a C major triad with a fourth note added on top. Cmaj7 adds B, a half step below the octave, and sounds settled and warm. C7 adds B flat, a whole step below, and leans hard towards the chord a fourth above it. One note apart, and opposite jobs.
- How can I tell whether a chord is major or minor?
- Listen to the distance from the lowest note of the stack to the middle one. Four half steps is the wide, bright third of a major chord; three half steps is the narrow, dark third of a minor one. The outer notes are a perfect fifth in both, so the middle note decides it by itself. You can also name any chord from its notes on the spot.
- What is a half-diminished chord?
- It is a diminished triad with an ordinary minor seventh on top: C, E flat, G flat, B flat. Pop and guitar books write it Cm7♭5, and jazz and classical analysis write it Cø7 with a slashed circle. Both spellings ask for exactly the same four notes.