Key signature

In <a href="/facts/Western_culture/rPbgAhzI">Western</a> <a href="/facts/Musical_notation/eubaB0AK">musical notation</a>, a key signature is a set of <a href="/facts/Sharp_(music)/dUgIJtHX">sharp</a> (♯), <a href="/facts/Flat_(music)/gS2acguR">flat</a> (♭), or rarely, <a href="/facts/Natural_(music)/tgpbcoP2">natural</a> (♮) symbols placed on the <a href="/facts/Staff_(music)/PldhTGvE">staff</a> at the beginning of a section of music. The initial key signature in a piece is placed immediately after the <a href="/facts/Clef/a3FBqdAf">clef</a> at the beginning of the first line. If the piece contains a section in a different <a href="/facts/Key_(music)/jo4UMbHp">key</a>, the new key signature is placed at the beginning of that section.
In a key signature, a sharp or flat symbol on a line or space of the staff indicates that the <a href="/facts/Note_(music)/spIQyV4T">note</a> represented by that line or space is to be played a <a href="/facts/Semitone/lVBsLYSA">semitone</a> higher (sharp) or lower (flat) than it would otherwise be played. This applies through the rest of the piece or until another key signature appears. Each symbol applies to comparable notes in all <a href="/facts/Octave/RA4gWvkV">octaves</a>—for example, a flat on the fourth space of the <a href="/facts/Clef/a3FBqdAf">treble staff</a> (as in the diagram) indicates that all notes notated as <a href="/facts/E_(musical_note)/n1RY9PGc">Es</a> are played as <a href="/facts/E%25E2%2599%25AD_(musical_note)/vdhauSmL">E-flats</a>, including those on the bottom line of the staff.
Most of this article addresses key signatures that represent the <a href="/facts/Diatonic_and_chromatic/gyD81SHE">diatonic</a> keys of Western music. These contain either flats or sharps, but not both, and the different key signatures add flats or sharps according to the order shown in the <a href="/facts/Circle_of_fifths/0aE2lkVq">circle of fifths</a>.
Each <a href="/facts/Major_scale/WtnkhIgv">major</a> and <a href="/facts/Minor_scale/MedkQtlE">minor</a> <a href="/facts/Key_(music)/jo4UMbHp">key</a> has an associated key signature, showing up to seven flats or seven sharps, that indicates the notes used in its scale. Music was sometimes notated with a key signature that did not match its key in this way—this can be seen in some <a href="/facts/Baroque_music/UgrJnyTq">Baroque</a> pieces, or transcriptions of traditional <a href="/facts/Mode_(music)/uzguYm9j">modal</a> <a href="/facts/Folk_music/yFHpeE7k">folk</a> tunes.

Key signature open-in-new

Key signature