In music, the term note has two primary meanings: 1) a sign used in musical notation to represent the relative duration and pitch of a sound; and 2) a pitched sound itself. Notes are the "atoms" of much Western music: discretizations of musical phenomena that facilitate performance, comprehension, and analysis (Nattiez 1990, p.81n9).

The term "note" can be used in both generic and specific senses: one might say either "the piece Happy Birthday to You begins with two notes having the same pitch," or "the piece begins with two repetitions of the same note." In the former case, one uses "note" to refer to a specific musical event; in the latter, one uses the term to refer to a class of events sharing the same pitch. image:'A' (PSF).png

Note name

Two notes with fundamental frequencies in a ratio of any power of two (e.g. half, twice, or four times) will sound very similar. Because of that all notes with these kinds of relations can be grouped under the same pitch class. In traditional music theory pitch classes are represented by the first seven letters of the Latin alphabet (A, B, C, D, E, F and G) (some countries use other names as in the table below). The span of notes between one pitch and another that is twice (or half) its frequency is called an octave. In order to differentiate two notes that have the same pitch class but fall into different octaves, the system of scientific pitch notation combines a letter name with an Arabic numeral designating a specific octave. For example, the now-standard tuning pitch for most Western music, 440 Hz, is named a′ or A4. There are two formal ways to define each note and octave, the Helmholtz system and the Scientific pitch notation.

Accidentals

, "Cmusic: sharpmusic: sharp" yields D, when D's sharp is in the signature. Assuming enharmonicity, it is possible that use of accidentals will create equivalences between pitches that are written differently. For instance, raising the note B to Bmusic: sharp is equal to the note C. Assuming the elimination of all such equivalences, however, the complete chromatic scale adds five additional pitch classes to the original seven lettered notes for a total of 12, each separated by a half-step.

Notes that belong to the diatonic scale relevant in the context are sometimes called diatonic notes; notes that do not meet that criterion are then sometimes called chromatic notes.

In musical notation, alterations to the seven lettered pitches in the scale are indicated by placing an accidental immediately before the note symbol, or by use of a key signature. The natural symbol (music: natural), can be inserted before a note to cancel a previously indicated flat or sharp (so as "Fmusic: natural" an F-sharp would become simply F).

Another style of notation, rarely used in English, uses the suffix "is" to indicate a sharp and "es" (only "s" after A and E) for a flat, e.g. Fis for Fmusic: sharp, Ges for Gmusic: flat, Es for Emusic: flat. This system first arose in Germany and is used in almost all European countries whose main language is not English or a Romance language.