Notes

Music names its notes with only seven letters: A B C D E F G. After G the alphabet starts over at A, higher up, and keeps repeating for as long as the instrument goes.

On the piano these seven letters are the white keys. Find the group of two black keys: the white key just to the left of that pair is always C. From there the white keys go C D E F G A B and then C again.

Play the seven letters in order and listen for the moment the pattern comes back to C. That is the whole keyboard in miniature. We will explain in the next section why the eighth note sounds like the first.

Every letter appears many times on the piano, so to say exactly which C we mean we add a number: C3, C4, C5. Two notes with the same letter, one number apart, are an octave apart: they sound like the same note, one higher and one lower.

The reference point is middle C, written C4. It sits near the middle of the keyboard, roughly under the maker's name. A full 88-key piano runs from A0 at the bottom to C8 at the top, a little more than seven octaves, so the octave numbers you will meet are 0 to 8.

Play C3, C4 and C5 one after another. You hear three different pitches, yet the ear insists they are all "C". That family resemblance is the octave, and it is the reason we only need seven letters.

A sharp (#) raises a note by one semitone (also called a half step): the distance from any key to the very next key, black or white. C# is the black key immediately to the right of C.

Name the five black keys this way, each from the white key on its left, and you get C# D# F# G# A#. Notice there is no E# or B# black key: to the right of E sits F, and to the right of B sits C, with nothing in between.

In note names the sharp comes right after the letter and before the octave number: F#4 is the black key just above F4. Play each white key and then its sharp to hear the small step up.

A flat (b) lowers a note by one semitone. Bb is the black key immediately to the left of B. The same five black keys, now named from the white key on their right, are Db Eb Gb Ab Bb.

Again two white keys have no black key below them: to the left of F is E, and to the left of C is B. So there is no Fb or Cb black key.

Every black key has two names. C# and Db are the same key and the same sound. Two names for one pitch are called enharmonic equivalents.

If they sound identical, why keep both names? Because a name says where the note comes from. F# is a raised F; Gb is a lowered G. When we build scales in a later chapter, the rule will be that every degree gets its own letter. So a scale that already has a G will call this key F#, and a scale that already has an F will call it Gb.

Seven white keys plus five black keys make twelve different notes, and then the pattern repeats an octave higher. Playing all twelve in order, one semitone at a time, is the chromatic scale.

By convention we spell it with sharps going up and flats going down, so the name of each note points in the direction we are travelling:

The chromatic scale is not a scale you will write many melodies with. It is the complete inventory. Every other scale is a selection from these twelve, and an octave is exactly twelve semitones wide.

The two smallest distances in music are the semitone (one key to the very next key) and the whole tone (two semitones, one key skipped in between).

Here is the detail that shapes everything later: most neighbouring white keys have a black key between them, so C → D, D → E, F → G, G → A and A → B are whole tones. But `E → F` and `B → C` have no black key between them. Those two white-key steps are only a semitone.

Those two narrow gaps are exactly what gives the white-key scale its character. In the next chapter every distance between two notes gets a name of its own, and from then on we will find notes by those names rather than by counting keys.

A note is a vibration, and its pitch is how fast that vibration repeats, measured in hertz (Hz), cycles per second. The tuning reference for most of the world is A4 = 440 Hz.

Go up one octave and the frequency doubles: A5 is 880 Hz. Go down one octave and it halves: A3 is 220 Hz. This 2:1 ratio is why octaves sound like the "same" note: the faster wave fits exactly twice inside the slower one.

Twelve equal semitones divide each doubling: every semitone multiplies the frequency by about 1.0595, and twelve of those multiplications make exactly 2.

Written music sits on a staff of five lines and four spaces, and a clef at the left tells you which note each line stands for. The treble clef is the one for higher notes, the right hand on the piano.

The treble clef is also called the G clef: its curl wraps around the second line from the bottom, and that line is G4. From there, lines and spaces alternate up the alphabet.

Middle C is not on the treble staff. It hangs just below it on a short extra line called a ledger line. Everything from E4 upward sits comfortably on the five lines.

The bass clef is the staff for lower notes, the left hand on the piano. Its two dots sit on either side of the fourth line from the bottom, and that line is F3, which is why it is also called the F clef.

Compare the two clefs: the bass staff covers G2 to A3, the treble staff E4 to F5. Between them sits a gap of a few notes, B3, C4 and D4, and middle C lives in the centre of that gap, just above the bass staff on its own ledger line.

Put the treble staff above the bass staff, join them with a brace, and you have the grand staff, the notation you see at the top of this page. It covers the whole central range of the piano in one picture.

Middle C (`C4`) is the hinge. It is written on a ledger line just below the treble staff or just above the bass staff. It is the same key either way. Notes above it usually go in the treble staff for the right hand; notes below it in the bass staff for the left.

Read straight through the grand staff from bottom to top and the alphabet never breaks: G2 A2 B2 … F3 G3 A3, then B3 C4 D4 in the gap, then E4 F4 … F5. Notes higher than F5 or lower than G2 simply get more ledger lines. Play a few notes in the composer and watch them land on the correct staff.

Here is everything in one sentence: music has twelve notes, they repeat in octaves, and every octave is twelve semitones wide. That is the complete map. The rest of this course is about how to travel it.

Next chapter we measure the distance between any two of these notes: those distances are intervals, and semitones and whole tones are the first two. After that, we choose seven of the twelve to make a scale, and stack notes from that scale to make chords.