Music theory The basics
Notes and the stave
Note names, the stave, the four main clefs, ledger lines, middle C, sharps and flats, and octave numbers like C4.
Practise this on its own page: Practise note names, Piano keys.
The musical alphabet
Western music uses just seven letter names: A, B, C, D, E, F and G. After G the letters start again at A, so the same names repeat from low notes to high notes.
Two notes with the same letter name that are twelve semitones (half steps) apart are an octave apart. A semitone (half step) is the smallest distance between two notes in Western music.
On a piano the black keys come in groups of two and three. The white key just to the left of a group of two black keys is always C, and the white key just to the left of a group of three is always F.
The stave (staff)
Music is written on a stave (called a staff in American English): five horizontal lines with four spaces between them. Notes sit either on a line or in a space, and higher notes are written higher up the stave.
On its own, a stave does not tell you which note is which. A clef at the start of the stave gives the lines and spaces their letter names.
The four main clefs
Each clef marks one line with a particular note, and all the other notes are counted from there. Treble and bass clef are the ones most beginners meet first.
| Clef | Marks | Lines | Spaces | Mainly used for |
|---|---|---|---|---|
| Treble (G clef) | G on the second line from the bottom | E G B D F | F A C E | Higher voices and instruments |
| Bass (F clef) | F on the second line from the top | G B D F A | A C E G | Lower voices and instruments |
| Alto (C clef) | C on the middle line | F A C E G | G B D F | Mainly the viola |
| Tenor (C clef) | C on the second line from the top | D F A C E | E G B D | Sometimes cello, bassoon and trombone |
Ledger lines, middle C and the grand stave
When a note is too high or too low to fit on the stave, short extra lines called ledger lines are drawn above or below it. The letter names carry on in the same order along these extra lines.
Piano music uses a grand stave (grand staff): a treble stave above a bass stave, joined on the left by a line and a brace. Middle C sits on one ledger line between the two staves, just below the treble stave or just above the bass stave.
Sharps, flats and naturals
These signs are called accidentals and are written just before a note. A sharp (#) means play the note one semitone higher, and a flat (b) means play it one semitone lower. A natural cancels a sharp or flat and brings the note back to its plain letter name.
A double sharp or double flat moves a note by two semitones. For example, F double sharp sounds the same as G, which shows that one sound can have more than one name.
An accidental affects that note and any later notes on the same line or space in the same bar. Once you pass a bar line, the accidental no longer applies, unless the note is tied across the bar line.
Octave numbers (scientific pitch notation)
To say exactly which C or which A you mean, musicians add an octave number to the letter. In this system, called scientific pitch notation, middle C is C4.
The number goes up by one each time you pass from B up to C. So the note just below middle C is B3, and the C an octave above middle C is C5.
The widely used tuning standard sets A4 (the A just above middle C) at exactly 440 vibrations per second, written 440 Hz. With that standard, middle C (C4) is about 261.6 Hz.