Every jazz student hears it in the first month, usually from someone who has stopped needing it. Know the rules, then break them. The sentence has been repeated so often it has worn smooth, and like most smooth sayings it is now quoted mainly for its second half. Breaking is the glamorous part. Nobody puts "know the rules" on a T-shirt.

This essay began as a reading of a lesson on the site Jazzadvice, which takes the saying seriously enough to ask what each word means. We have taken it further, because the argument deserves more than a page: it deserves a keyboard, a chorus of blues, and a test you can fail in private. Everything below that makes a sound needs a tap and a speaker. Everything else is just reading.

The claim, in one sentence: the second half of the saying is worthless without the first, and almost nobody who quotes it has done the first.

"Know" is the word doing all the work.

The Jazzadvice lesson turns on a small scene from a summer camp. A student is asked whether he knows a particular scale and says yes, meaning that he can name its notes. The instructor then plays that scale on the trumpet in every register, in thirds, in fourths, in patterns, up to the top of the horn and back, at tempo, without looking at anything. The student, it becomes clear to everyone in the room, did not know the scale. He knew its definition. The distance between those two states is the entire subject.

Try the distance yourself. The keyboard below holds one scale, C major, the first thing anyone learns. Naming it takes a second. Then listen to what the instructor meant.

Notice what happened between the first button and the last. Nothing was added to the scale. The notes never changed. What changed was the relationship between the player and the notes: from a list that can be recited to a shape that can be moved through at will, in any direction, at any speed, without the mind having to attend to it. Musicians have a word for the moment a scale stops being a list. They say it is under the fingers. The phrase is exact. It has left the head and gone somewhere faster.

Everything in jazz that looks like freedom depends on things being under the fingers. Improvisation at a hundred and eighty beats a minute leaves no time to think about where the notes of a scale are; the thinking has to have been done years earlier, so that in the moment there is only choosing. The player who is still finding the scale cannot choose. He can only arrive. That is why the instructor's demonstration was not showing off. It was defining terms.

You can only leave out what you can already hear.

The rules of jazz are mostly called the changes: the sequence of chords a tune moves through, the harmonic floor a soloist stands on. Learning a tune means learning its changes so well that you can hear them with the band silent. This is not a figure of speech. Here is a twelve-bar blues in C, the most common set of changes in the music. Play one chorus with the bass and the chords. Then play the second chorus, in which the band stops and only a melody is left.

The second chorus is the whole argument in ninety seconds. The changes are still there. They are in you, or they are not, and the silence reveals which. When Ornette Coleman stopped playing over chord changes in 1959 the shock was not that he had removed something. It was that everyone on the bandstand and most people in the room could still hear what was gone. The absence was legible. It was, in a sense, the loudest thing on the record.

Every famous rule-break named the rule as it broke it.

The lesson lists the usual saints: Armstrong, Parker, Coltrane, Coleman, and, reaching outside jazz, Debussy and Schoenberg, who dismantled tonality only after spending their youth inside it. What the list shares is not audacity. It is sequence. Read the biographies in order and the same shape appears every time: years of a discipline, then a departure from it that only makes sense because of the years. Tap through them.

Read them as a set and the pattern is impossible to miss. Not one of these is a stranger wandering in. Each is a fluent speaker choosing, in public, to say something ungrammatical, and the meaning comes from the fluency. Coleman's freedom is audible because Coleman could play the changes. Coltrane's late records are unbearable to some listeners and overwhelming to others, but nobody has ever accused them of not knowing where the chords were; Giant Steps settled that question in advance, permanently. A rule-break is legible only against the rule, which means the rule is inside the rule-break, doing most of the work.

What playing without rules actually sounds like.

The Jazzadvice lesson makes its sharpest point with an observation from the pianist Brad Mehldau about the players in his own school band who had never listened to the music. Asked to improvise, they all did the same thing: they ran the scale up and down. Not because they lacked talent, and not because they lacked freedom. They had nothing but freedom. What they lacked was a language, and without one the free choice of every note produced the same result in every mouth.

This is the part of the saying nobody quotes, and it is the important part. The lesson's claim is not moral; it is acoustic. Freedom without grammar does not produce originality. It produces convergence. Here is what that sounds like, generated fresh each time, and beside it what a phrase sounds like when someone has learned the language.

Press the first button a few more times. The notes differ; the solo does not. Every run sounds like every other run because there is only one way to have no ideas, and the scale, left alone, will supply it. Noise is the most conventional sound there is. The rules are not the enemy of a personal voice. They are the only thing that makes a personal voice distinguishable from everybody else's untrained one, and the players who sound most like themselves are, without exception, the players who learned the most.

What the rules are, and what it costs to learn them.

The lesson ends where honest lessons end: with a list of things that take years. Harmony, technique, the ear, the recordings, the history. There is no shortcut on the list and the site does not pretend there is. Here is the same inventory, in the terms a working musician would use, followed by a test.

Harmony, until it is not theory

Chord construction, voice leading, substitutions, the cycle of fourths in every key. Not as facts that can be explained, but as sounds that can be recognised in the dark. Theory is finished when you no longer need it.

The instrument, until it disappears

Scales, arpeggios and patterns in all twelve keys, at every tempo, until the horn or the keyboard stops being a thing you operate and becomes a thing you speak through. This is the camp scene, extended over a decade.

The ear, until it leads

Hearing a chord and naming it; hearing a line and playing it back; hearing the changes, as in the second chorus above, with nothing there. The ear is the last thing to catch up and the only thing that matters on the bandstand.

The records, until they are in you

Transcription: learning solos by ear from the recordings, note for note, until the vocabulary of Armstrong and Parker and everyone since is under your own fingers. This is how the language is actually transmitted. There is no book, because the book would be the records.

The history, until you know where you are standing

Who did what, when, in reaction to whom. Not as trivia, but as the map that tells you which rule you would be breaking and whether somebody already broke it better in 1945.

That is a lot. Here is a way to find out where you are with one tune. Pick any standard you think you know, Autumn Leaves, All the Things You Are, a blues, and answer honestly.

Five arguments to have with us.

A journal that only concludes is a lecture. These are the places where this essay is least sure of itself. Take any of them up, in writing, and we will answer.