In music, a note is either a unit of fixed pitch that has been given a name, or the graphic representation of that pitch in a notation system, and sometimes its duration, or a specific instance of either, so one can speak of "the second note of Happy Birthday" for example. The general and specific meanings are freely mixed by musicians, although they can be initially confusing: "the first two notes of Happy Birthday are the same note", meaning, "the first two sounds of Happy Birthday have the same pitch." A note is a discretization of musical or sound phenomena and thus facilitates musical analysis (Nattiez 1990, p.81n9).

In English, the notes are given 7 letter names: A, B, C, D, E, F, and G. Each letter name is assigned to a specific pitch regardless of the octave in which the pitch resides. Notes are used together as a scales or tone row. However, because there are actually 12 notes needed by diatonic music, the 7 letter names can also be given a modifier.

The two main modifiers are sharps and flats which respectively raise or lower the pitch of a note by a semitone. These are used to create the additional five notes necessary to complete the chromatic scale. The sharp symbol is ♯ (similar to the pound symbol, #), the flat symbol is ♭ (similar to a lower-case b).

In music notation, a note is sharpened or flattened (raised or lowered) by placing a sharp symbol or flat symbol directly in front of the note. When using letters, the symbol follows the letter, as in A♯ for the note A sharp.

Modifiers can be set for the duration of a piece at the front of the staff immediately after the clef and before the time signature, in which case they form the key signature: for example, a sharp symbol on the F line indicates that every F in the staff is to be understood as an F♯ (F sharp). Modifiers which occur during the piece and alter a specific note are called accidentals. An accidental stays in effect until either the end of the measure, or a natural is encountered.

Also common are double flats and double sharps, which alter the pitch of the note by a whole step, rather than a half step. There is also a natural accidental in notation, which undoes the change made by a previous accidental or the key signature itself.

When notes are written out in a score, each note is assigned a specific vertical position on a staff position (a line or a space) on the staff, as determined by the clef. Each line or space is assigned a note name, these names are memorized by the musician and allows him or her to know at a glance the proper pitch to play on his or her instrument for each note-head marked on the page.

The staff above above shows the notes C, D, E, F, G, A, B, C and then in reverse order. There are no sharps or flats at the beginning of the staff, indicating that this is the key of C major. (A key signature with no sharps or flats could also denote the key of A minor, which is the relative minor of C major.)

The approximate frequencies of the notes above are:

• C: 262Hz
• D: 294Hz
• E: 330Hz
• F: 349Hz
• G: 392Hz
• A: 440Hz
• B: 495Hz

The frequency of a note doubles per octave—one A is 440Hz and the A an octave higher is 880Hz.

History of note names

Music notation systems have used letters of the alphabet for centuries. The 6th century philosopher Boethius is known to have used the first fifteen letters of the alphabet to signify the notes of the two-octave range that was in use at the time; it is not known whether this was his devising or common usage at the time; nonetheless this is called Boethian notation.

Following this, the system of repeating letters A-G in each octave was introduced, these being written as minuscules for the second octave and double minuscules for the third. When the compass of used notes was extended down by one note, to a G, it was given the Greek G (G), gamma. (It is from this that the French word for scale, gamme is derived, and the English word gamut.)

The remaining five notes of the chromatic scale (the black keys on a piano keyboard) were added gradually; the first being B which was flattened in certain modes to avoid the dissonant augmented fourth interval. This change was not always shown in notation, but when written, B? (B flat) was written as a Latin, round "b", and B— (B natural) a Gothic b. These evolved into the modern flat and natural symbols respectively. The sharp symbol arose from a barred b, called the "cancelled b".

In parts of Europe, including Germany, the natural symbol transformed into the letter H: in German music notation, H is B— (B natural) and B is B— (B flat).

Notes can be worth different fractions of a beat; to find this, multiply the note value (e.g. half is 1/2) by the bottom number of the time signature. The note names are:

Category

• Musical notation