Musical note

In music, a note is an abstract concept used to refer both to a unit of fixed pitch which has been given a name, and also the graphic representation of that pitch in a notation system. A note can also be a specific instance of either, so one can speak of "the second note of Happy Birthday to You" for example.

In English, the notes are given 7 letter names (A, B, C etc...). 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 raise or lower, respectively, the pitch of a note by a semitone. These are used to create the additional five notes necessary to complete the chromatic scale. In notation, a note is designated as being sharp by placing a sharp symbol (#) directly in front of the note to be played sharp. A flat is designated by a flat symbol (similar to a lower case 'b').

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. Modifiers which occur during the piece are called accidentals.

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 restores a note to the pitch specified by its Key.

When notes are written out in a score, each note is assigned a specific vertical position on either a line or in a space on the staff. 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.

http://meta.wikipedia.com/upload/c_maj.png

A 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.