Sound and pitch

Pitch is the property that lets you say one sound is higher than another. It comes from how fast the air is vibrating: faster vibration, higher pitch. That speed is the frequency.

Pitch is what a note carries, and what a melody is made of. Everything on the reading side — the staff, the clef, the lines and spaces — exists to write pitch down.

Not every sound has a definite pitch. A snare drum or a handclap has a pitch you cannot easily sing back; a piano key or a sung vowel has one you can.

A vibrating string, a column of air, a loudspeaker cone: each moves back and forth a certain number of times per second. That count is the frequency, written in hertz.

The A above middle C is usually tuned to 440 Hz, and most tuners default to it. Double a frequency and you get the same note name one octave higher: 880 Hz is also an A.

You never need to think in hertz to play music. It is here because it explains why the octave feels like the same note, and why the semitone is the size it is.

The word does two jobs, which is worth knowing early because both are common.

A note is a sound: something with a pitch you could sing, lasting a certain duration. When someone says "play a note", this is the meaning.

A note is also a symbol: the oval written on the staff, whose vertical position gives the pitch and whose shape gives the duration. When someone says "read the notes", this is the meaning.

A note has a name — C, D, E and so on — and that name is not quite the same thing as the sound. F sharp and G flat are one key on a keyboard and two different notes, because they behave differently in the key they belong to.

Seven names cover every note there is: A, B, C, D, E, F, G. Past G you start again at A, one octave higher. In many countries — Brazil among them — the same seven are called dó, ré, mi, fá, sol, lá, si. Both are naming systems for the same sounds, and this app lets you choose which one it shows.

An accidental can be added to a name: C sharp, B flat. An octave number can be added too — C4 is middle C, C5 is the C above it.

The names matter more than they look. Because there are seven names and twelve semitones in an octave, some neighbouring names are a tone apart and some are only a semitone apart, and that unevenness is where scales and key signatures come from.

Sing a note, then sing the same note as high as you comfortably can. The second one is an octave above the first. It sounds so much like the first that both get the same name.

The reason is arithmetic: the higher one vibrates at exactly twice the frequency. Every octave up doubles it again.

On a keyboard an octave is twelve keys, counting black and white alike. Note names get a number to say which octave they are in — C4, the C nearest the middle of a piano, is called middle C.

Put a finger on any piano key and move to the neighbouring key, ignoring colour. That distance is a semitone — also called a half step.

Twelve of them make an octave. That is the whole system: every note in ordinary Western music sits somewhere on that ladder of twelve.

Most neighbouring white keys have a black key between them, so they are a tone apart. Two pairs do not: E and F, and B and C. Those two are a semitone apart with nothing in between, and that irregularity is the reason scales need sharps and flats at all.

Written down, a semitone up is a sharp and a semitone down is a flat.

A tone is simply two semitones stacked. On a keyboard it is usually two white keys with a black key hiding between them: C to D, D to E, F to G, G to A, A to B.

The exceptions are the pairs with no black key between them — E to F and B to C — which are a semitone, not a tone.

The major scale is built entirely out of these two sizes, in a fixed order: tone, tone, semitone, tone, tone, tone, semitone. Learn that pattern and you can build a major scale from any starting note.

A caution about the word: in Portuguese tom means both this distance and, loosely, the key a piece is in ("em que tom?"). They are different ideas that share a word.

An interval is named by two things at once. A number, counted along the note names from one to the other, inclusive: C up to E touches C, D, E, so it is a third. And a quality — major, minor, perfect, augmented, diminished — which pins down the exact number of semitones.

So C to E is a major third (four semitones) and C to E flat is a minor third (three). Same number, different quality, and quite different sound.

This is why spelling matters. C to E flat and C to D sharp are the same two keys on a piano, but the first is a third and the second is a second, and they belong in different keys.

Intervals are the raw material of melody and harmony alike: one after another they make a tune, sounded together they make a chord.

A melody is one note after another, arranged so that the ear follows them as a connected line rather than a list. What connects them is mostly the intervals between them and the rhythm they arrive in.

Good melodies tend to move mostly by step, use leaps sparingly and turn back after them, and come to rest on stable notes — very often the tonic.

A melody divides into phrases, the way prose divides into sentences. Sing one and you will breathe at the phrase boundaries without being told where they are.

Phrases are how a melody is organised in time. A phrase states something and then arrives somewhere, and the arrival is what makes it feel finished or unfinished.

A phrase ending on the tonic sounds closed, like a full stop. One ending elsewhere — very often on the fifth degree — sounds open, like a comma, and asks for an answer. Composers pair them constantly: an opening phrase and a closing one.

You can usually hear where a phrase ends before you can explain why. Singing along and noticing where you would breathe is a reliable test.