Accidentals and the key signature
The black keys have no place of their own on the staff. Three signs, one cluster at the start of the line, and two rules that hand you every key.
The two previous lessons covered the white keys. But your instrument has another thirty-six black keys, and so far they have had no representation on the page whatsoever.
The answer is elegant and irritating at the same time: the black keys have no position of their own on the staff. They are written as their white neighbor, with a small sign attached that says "hold on, not that key — the one next to it".
Three signs, and that is the whole vocabulary.
A sharp looks like a hash mark, and it says: take the written note and move one key to the right. Not one white key — one key, whatever that key turns out to be. If the neighbor on the right is black, black is what you play.
A flat looks like a lowercase letter b, and it says exactly the reverse: one key to the left.
The natural sign looks like a small square with two tails hanging off it, and it cancels a sharp or a flat that was in force, putting you back on the plain white key.
The sign is written before the note, to its left, and it stays in force until the end of the bar. Another note at the same pitch inside that same bar gets the same treatment automatically, with no need to repeat the sign. After the bar line, everything resets.
The black key between C and D is called C sharp if you arrived at it from below, and D flat if you arrived from above. The very same key. The very same sound. Two names.
This is not a bug and not needless complication. The name depends on the direction the sound is coming from and on the job it is doing at that moment, which is why a composer writes C sharp in one place and D flat in another for the identical key — he is handing you information about the harmony, not just about your finger.
For the purposes of playing, at this stage: it makes no difference at all. You press the same key either way.
And here is the surprise that closes the circle: between E and F, and between B and C, there is no black key at all. Which is why E sharp is simply F, and B sharp is simply C. Look down at the instrument and you will see it — between E and F sit two white keys pressed right up against each other, with nothing whatsoever in between. That gap is what creates the pattern of two blacks and three blacks you are already using to navigate.
Now for the practical part. If a song leans on the same black keys over and over, writing a sign in front of every single note would turn the page into an unreadable thicket.
So the signs are collected at the start of the line, immediately after the clef, and written once. This is called the key signature, and it says: all of these notes, in every octave, for the length of the whole song, are played with the sign — unless something says otherwise.
| Key signature | Major key | What you play differently |
|---|---|---|
| Empty | C | Nothing at all, it is all white |
| One sharp | G | Every F becomes F sharp |
| Two sharps | D | F and C both become sharp |
| One flat | F | Every B becomes B flat |
| Two flats | B flat | B and E both become flat |
Notice the most useful rule this table carries: the key signature is the first thing you read on a page, before the first note. People skip past it and start playing, and then the song sounds slightly crooked and nobody can work out why. Five seconds of looking spares you all of that.
It is also why it pays to start in C major: it does not carry one single sign, so everything you learned in the two previous lessons works there with nothing added on top.
The table above covers five keys out of fifteen. Memorizing all fifteen is a waste of effort, and unnecessary besides: there are two rules that hand you the lot.
When there are sharps: the last sharp in the group, the rightmost one, sits a half step below the name of the key. A signature with F sharp on its own — the note above F sharp is G, so this is G major. A signature with F sharp and C sharp — above C sharp is D, so this is D major.
When there are flats: the second-to-last flat is the name of the key. A signature with B flat and E flat — the second-to-last one is B flat, so this is B flat major. The single flat is the one exception worth simply memorizing: B flat alone is F major.
Those two rules hold for all fifteen keys, without one exception between them. Two minutes of practice with them is worth more than an hour of memorization.
Here is a point that surprises every beginner, and is worth knowing in advance.
C major is the easiest key to read, because the page is clean of signs. It is nowhere near the easiest to play, because five white keys in a row leave the hand flat and smeared out across them. Keys that use black notes give the long fingers a raised place to land on, and the hand arches by itself.
Which is why experienced pianists feel at home precisely in the keys with four and five sharps, while beginners assume that is showing off. It is not — it is simply more comfortable for the hand.
That said, it is a second-year concern. In the first year reading is the bottleneck, so you start where the page is simple. The fingering that lets you play a whole scale without stopping is taken apart in the next lesson.
Sometimes you will see a sharp or a flat that is not in the key signature at all but sitting in the middle of the line. That is called an accidental, and it always means something.
It usually signals one of two things. Either the song has moved temporarily into a different key — a very common trick in choruses, and the source of that feeling of lift — or it is a decorative note, a pinch of spice, put there to sharpen the sound that comes after it.
In both cases the practical rule is identical: play exactly what is written, even when it feels strange. Plenty of beginners quietly correct it back to the "right" note for the key, and erase the precise moment the composer was reaching for.
And if the same sign keeps coming back through the whole song, it is not accidental at all anymore — it is a sign that the song is in a different key from the one you assumed. Worth going back to the top of the page for a second look.
If you have read the lesson on scales, you already know that a major scale is built on a fixed set of intervals: whole, whole, half, whole, whole, whole, half.
The key signature is precisely the output of that rule. Start the sequence on G and keep the same intervals, and you will find you must have an F sharp for it to come out right — which is why G major carries one sharp. Start on F and you will find you must have a B flat. Nobody sat down and chose any of this; it is what falls out of the arithmetic.
At the piano this is visible to the eye in a way it is on no other instrument: whole-whole-half is literally a pattern of keys, and you can see it lying there in front of you. Building chords out of those scales is taken apart in the musical sandwich.
| What is happening | The likely cause | The fix |
|---|---|---|
| The song sounds crooked from note one | You skipped the key signature | Read it before anything else on the page |
| The sign is forgotten mid-bar | You think it applies to one note | It holds until the end of the bar |
| Hunting a black key between E and F | Assuming there is one between every pair | There is not. Nor between B and C |
| Sharps and flats keep getting swapped | Trying to memorize the shapes | Sharp goes right, flat goes left. Always |
| Two names for one key is confusing | Looking for a rule that settles it | For playing they are identical; the name is harmony |
| The sign is ignored after the bar line | No, that is how it is supposed to work | A bar line resets. It is not a flaw in the page |
That is everything the page has to say. From here you move from what you read to what your hands do, and that is the technique course.