Theory in Styles

Chord-scale theory is the practice of pairing every chord in a progression with a scale that contains that chord’s notes, so that a player improvising over the chord has seven pitches to draw on and a stated reason for each of them rather than four chord tones and guesswork.

The move it makes is small and it changes everything. A chord symbol names four notes; a chord-scale names seven, of which four are the chord and three are the colour. The chord tones say what the chord is and the other three say what it feels like. Over Dm7Play the pairing is Dorian, and the note that makes it Dorian is the sixth degree, B — the difference between the first two clips above and nothing else. Swap that B for a B♭ and the same chord is being read as Aeolian, which is darker, more settled, and much less like jazz. One chord and one scale paired together like that is a chord-scale relationship, which is the phrase jazz teaching uses for the individual pairing; the doctrine that every chord in a tune has one is the theory.

What makes the system teachable is that the seven pairings in the table are not choices at all: play a major scale and take the chord and the scale from the same degree, and the pairing falls out. Dorian over the second-degree chord, Mixolydian over the fifth, Lydian over the fourth. The choices begin one step later, when a player takes a scale from somewhere other than the key — Lydian over Cmaj7Play to raise the fourth, or an altered scale over a dominant — and those are decisions about colour made chord by chord.

The one thing to carry away is the last column. A scale note that is not itself part of the chord and sits a half step above one of its notes will beat against it every time it is sounded with it, which is why jazz teaching calls such notes avoid notes and tells beginners to pass through them rather than land on them. That is not a prohibition. It is a description of what the interval does, and a player who knows which note it is can use it on purpose — what varies between styles is only whether the roughness is heard as a fault or as a resource.

Jazz harmony is the harmonic practice of jazz: chords built past the seventh into ninths, elevenths and thirteenths, dominant chords whose ninths and fifths are raised or lowered to sharpen their pull, and progressions assembled almost everywhere out of the two-chord approach that ends a phrase.

Everything in it is an intensification of something the harmony chapters already built. Chapter 10 stacked thirds and stopped at the seventh; jazz keeps stacking, and the ninth, eleventh and thirteenth are simply the next three. Chapter 14 reached outside the key for a dominant aimed at a chord other than home; jazz does that between almost every pair of chords in a tune. What is genuinely new is density and rate. A standard changes chord twice a bar for thirty-two bars, and every one of those chords carries four to six notes.

The unit the whole practice is built on is the pair in the fourth row of the table: a minor seventh chord on the second degree, then the dominant seventh on the fifth, then home. Learn to hear those two chords and you can hear where a tune is going, because a standard that visits four keys in thirty-two bars announces every one of them the same way. Bebop players wrote new tunes over the chords of old ones and inserted extra pairs wherever a bar could be spared, which is why the repertoire sounds like one long chain of them.

The substitution in the third row is the neatest trick in the book and it takes one sentence to explain. A dominant seventh chord pulls because of two notes a tritone apart — its third and its seventh — and a tritone divides the octave in half, so that same pair of notes is the third and seventh of a second dominant chord, the one a tritone away. Play that second chord instead and the pull survives intact while the bass slides down a half step into the arrival instead of leaping down a fifth.

Loop-based harmony is harmony built from a short chord pattern that repeats without a break: the same two, three or four chords in the same order, played round and round, with nothing inside the pattern marking an end and nothing to distinguish the last time round from the first.

Producers and songwriters rarely name the practice at all; what they name is the object. A chord loop is the thing itself — four bars of chords on a timeline, dragged, copied and stretched under everything else — and most writing about pop harmony is writing about chord loops rather than about the habit of building from them. Popular music has always been simpler harmonically than jazz, but the difference this section is about is not simplicity. It is punctuation. A progression in Chapter 11 was a sentence: it set out, it created an expectation, and a cadence at the end settled it. A loop has no cadence strong enough to close, and the four-chord pattern almost every reader has heard a thousand times is arranged so that the strongest one — the chord on the fifth degree followed by the home chord — never occurs. What the wrap does make is the other kind: the fourth-degree chord falling to the first, which Chapter 11 called a plagal cadence and described as a benediction rather than a conclusion. It settles the four bars about as firmly as an amen settles a hymn, which is to say not firmly enough to stop them going round again. The pattern is built to have no audible seam, because a seam is where a listener would notice the repetition.

That leaves the question of where home is, and the answer is that the chords do not decide it. The first two rows of the table are the same four chords entered at two different points, and each version has its own name in the literature because each sounds like a different progression. What settles it is where the bar line falls, which chord the singer lands on, where the bass sits and where the loop is cut on the timeline — all of them arrangement decisions, which is why the same four chords carry a triumphant chorus in one record and a lament in another.

One consequence is worth stating plainly, because it disappoints people who come to pop from the harmony chapters. There is frequently nothing to analyse. A track can run four chords for three minutes without a single event a Roman numeral would capture, and everything that happens to it — the parts entering and leaving, the filter opening, the drums dropping out before the chorus — happens somewhere other than the harmony. Chapter 16 gave that arrangement its plan; this section only removes the expectation that the chords will supply one.

A DAW — a digital audio workstation — is the program a piece of music is assembled in: a timeline of parallel tracks into which audio recordings and note events are drawn, edited, arranged, processed and mixed, with the whole arrangement editable after the fact.

The DAW grew out of the sequencer, which is not another name for it: the hardware boxes of the 1980s and the software descended from them recorded and replayed note events and never touched audio at all, and the note editor at the centre of a modern DAW is what is left of one. Most of this course is already inside that editor, under other names. The piano roll is the clearest case: a grid with pitch running up the left-hand edge, one row per key, and time running along the bottom. Every row is a half step, so the rows are the twelve notes of Chapter 2 and nothing else; a note is a rectangle whose vertical position is its pitch and whose width is its length. That is a staff with the scale steps replaced by half steps and the note values replaced by lengths — which is why an accidental is a decision on a staff and merely a different row in a DAW, and why nothing in a piano roll can tell you whether a black key is a G♯ or an A♭.

The grid behind the notes is metre. Quantising snaps every note to the nearest grid line, and a swing or shuffle setting then moves the off-beat divisions later by a percentage — 50% leaves them exactly halfway, and settings between 55% and 66% approach the long-short division that Chapter 15 called swing, with 66% landing on the triplet. The second clip above is that triplet division exactly: each beat divided into three, struck on the first third and the last, with the first hit holding through the middle one. Nothing about it is a production technique. It is a rhythmic convention several centuries old, exposed as a slider.

The gap between the two vocabularies is worth naming, because it is where most confusion about whether producers "need theory" comes from. A DAW knows pitch and time and knows nothing else: it has no idea what key a piece is in unless told, cannot tell a chord from four simultaneous notes, and will let a writer draw anything at all. The theory in this course is not a constraint the software imposes. It is the set of names for what is already on the screen, and the value of having them is that a name is something you can reason about and a shape you happened to draw is not.

The Western tonal tradition is the body of music this course’s harmony chapters describe: music built from twelve equally spaced pitches, organised around a key, harmonised in chords stacked in thirds, notated on a staff, and shaped by cadences that settle what earlier chords left owed.

That is a description of one tradition and not of music. Everything Chapters 10 to 14 say about chords, keys, functions and cadences is stated inside it, and none of it is a law that other music breaks. The table above names five traditions, each of which organises music with something the course has no symbol for: pitches between the keys of a piano, tunings that differ from one ensemble to the next, several simultaneous groupings of time with no shared bar line, a framework that carries obligatory phrases and ornaments rather than just a set of notes. None of these is a simpler system or a less developed one. Several are older than tonal harmony and at least as intricate, and all of them are studied for a lifetime by the people who play them. A tuning that makes a different compromise from equal temperament is not out of tune; it is tuned to something else.

The blues row is the useful one to sit with, because it is not distant at all. The blues is the parent of almost everything in this chapter’s first four sections, and it does two things the harmony chapters cannot describe. Its sung thirds and sevenths sit between the flattened and the natural note and slide, so the printed page rounds them to the nearest key and loses the whole expressive point. And its home chord is a dominant seventh, which Chapter 11 defines as a chord whose job is to pull elsewhere. A theory that declares the blues wrong has told you something about the theory.

None of that makes the course’s vocabulary useless outside its home — it makes it a vocabulary rather than a physics. The honest way in to a tradition you do not know is to ask what it organises music with before reaching for chords and keys, to name what your own description is dropping, and to learn the tradition’s own words for its own things. That question — what does this music organise itself with? — is where a guide to any particular genre has to begin, and so does the last chapter of this course.