Talk:Key signature

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7+sharps/flats, Modes

The article explains that the seven-sharp and seven-flat key signatures are rare but they have nonetheless been used. Why have they? Also, the article doesn't explain how modes play into the whole thing. I would imagine that F lydian uses the same key signature as C major, right?

--Furrykef 05:16, 17 May 2004 (UTC)

I'll try to explain here: Lets assume that a large scale piece is "in A major". If a section of that piece takes place on the mediant, and is in major, it would "correctly" be notated in C# major, with seven sharps. However, this is fairly rare, and more rare still considering subsidary key areas are often not notated with a change of key signature and that this change could be notated or enharmonically ("incorrectly") as Db major. Hyacinth 20:55, 18 May 2004 (UTC)

There may also be more mundane reasons; the Bach prelude and fugue cited in the article, for example, is notated in C sharp major rather than D flat major because (if I remember rightly) Bach took an old piece he had written in C major and just stuck seven sharps in the key signature to put it in the required key - much easier than re-notating the whole thing in D flat major.

Incidentally (a bit off-topic this), I've been looking at Chopin's mazurkas for fun, and noticed that in Opus 6, No. 2, there is a passage which is notated in G sharp major - eight sharps, that is, seven sharps and then F sharp again making F double sharp. This happens because G sharp major is the dominant parallel major of the piece's home key, C sharp minor. Of course, this isn't expressed in a key signature, but it's sort of interesting anyway, I think. --Camembert

Proposed outline

1. Intro: In music and musical notation, a key signature is a series of sharps or flats placed on the musical staff.
2. Indicates:
   1. A key signature indicates which notes or pitches are to be played one semitone sharp or flat. The "standard" against which notes are raised or lowered are the natural or white keys of the musical keyboard.
   2. Despite being called the "signature" of a "key", or tonic, it does not indicate, by itself, the Key, mode, or scale. However, if one knowns the key or tonic and the key signature then one can deduce the scale or mode.
   3. Accidentals are flat, sharp, or natural signs outside of a key signature. They may appear throughout a score. These override the key signature for the duration of the bar they occur in. Thus a written F, in key signature with F#, will be played F# unless it has an accidental natural sign immediately preceding it and any written Fs in that octave will be played as F#s until the next measure.
   4. During a modulation or change of key, the key may be temporarily different than the one still indicated by the key signature, or the key signature may change also.
3. History
4. Purpose: The purpose of key signatures is to avoid having to write sharps and/or flats before every note which would require one. The lines and spaces of the musical staff represent the white keys of a piano. This represents the C major and A minor scales and all modes beginning on the appropriate pitches. However, if one wishes to write in another scale, such as G major, one would need to write a sharp sign before each F that one used. Rather than do this, a key signature consisting of one sharp on the line for F, is added to the beginning of the score. Thus key signatures are a convenience of notation in tonal music, but are less usual and thus less frequently found in atonal music.
5. Design
   1. Standard:
      1. Key signatures are generally written immediately after the clef at the beginning of a line of musical notation, although they can appear in other parts of a musical score.
      2. They contain only sharps or flats and only in the order of the circle of fifths
   2. Non-standard: Nonstandard key signatures not included in the chart below are sometimes used by composers. One example being the key signature to Frederic Rzewski's song "God to a Hungry Child" (lyrics by Langston Hughes), which features Bb, Eb, and an F# in one key signature but which starts in the key of D with a D major chord.
6. misc: from F to B, the set of notes used in C Major or A Minor scale.