Editing Fugue (section)

===Exposition===<!--[[Call and response (music)]] links directly here.-->
{{Further|Exposition (music)}}

A fugue begins with the exposition of its subject in one of the voices alone in the [[tonic (music)|tonic]] key.<ref name = "oxfcomp">
G. M. Tucker and Andrew V. Jones, "Fugue", in ''The Oxford Companion to Music'', ed. Alison Latham (Oxford and New York: Oxford University Press, 2002). {{ISBN|0-19-866212-2}} {{cite book |url=http://www.oxfordreference.com/views/ENTRY.html?subview=Main&entry=t114.e2723|title=Oxford Reference Online, subscription access|isbn=978-0-19-957903-7|access-date=2007-03-16|last1=Latham|first1=Alison|year=2011|publisher=Oxford University Press }}</ref> After the statement of the subject, a second voice enters and states the subject with the subject transposed to another key (almost always the [[Dominant key|dominant]] or [[Subdominant key|subdominant]], with the latter being less common), which is known as the ''answer''.<ref>{{harvnb|Gedalge|1964|p=12}}</ref><ref>{{cite book | first = R. O. | last = Morris | title = Contrapuntal Technique in the Sixteenth Century | location = London | publisher = Oxford University Press | year = 1958 | page = 47 }}</ref> To enable a natural harmonic progression, the answer may also be altered slightly (usually by changing one or a few notes near the beginning). When the answer is an exact transposition of the subject into the new key, the answer is classified as a ''real answer''; alternatively, if the intervals of the subject are altered in any way, the answer is a ''tonal answer''.<ref name = "oxfcomp" />

{{Image frame|content=<score sound="1">
\new PianoStaff <<
  \new Staff \fixed c' {
    \key g \minor
    R1 |
    r2 r8 \once \override NoteHead.color = #blue g bes d |
    cis4 d r8 e16 f g8 f16 e |
  }
  \new Staff {
    \clef bass
    \key g \minor
    r8 \once \override NoteHead.color = #red d' ees' g fis4 g |
    r8 a16 bes c'8 bes16 a bes4 g |
    r8 a16 g f8 g16 a bes8 g e cis' |
  }
>>
</score>|caption=Example of a tonal answer in [[Johann Sebastian Bach|J.S. Bach's]] [[Prelude and Fugue in G minor, BWV 861|Fugue No. 16 in G minor, BWV 861]], from the ''[[Well-Tempered Clavier]]'', Book 1. The first note of the subject, D (in red), is a prominent dominant note, demanding that the first note of the answer (in blue) sound as the tonic, G.}}

When the subject begins with a prominent dominant note, or when there is a prominent dominant note very close to the beginning of the subject, a tonal answer is usually necessary.<ref name="oxfcomp" /> To prevent an undermining of the fugue's [[key (music)|key]], this note is transposed up a fourth to the tonic rather than up a fifth to the [[supertonic]]. For the same reason, it is possible for the answer of such a subject to be in the subdominant key.<ref name="Verrall-1966-p12">{{harvnb|Verrall|1966|p=12}}</ref>

During the answer, the voice in which the subject was previously heard accompanies with new material. If this new material is reused in later statements of the subject, it is called a ''[[countersubject]]''; if this accompanying material is only heard once, it is simply referred to as ''[[free counterpoint]]''.
[[File:Interval Inversion.jpg|thumb|400px|The interval of a [[Fifth (interval)|fifth]] inverts to a [[Fourth (interval)|fourth]] (dissonant) and therefore cannot be employed in [[invertible counterpoint]], without preparation and resolution.]]
The countersubject is written in [[invertible counterpoint]] at the octave or fifteenth (two octaves).<ref>{{harvnb|Gedalge|1964|p=59}}</ref> The distinction is made between the use of free counterpoint and regular countersubjects accompanying the fugue subject/answer, because in order for it to be heard accompanying the subject in more than one instance, the countersubject must be capable of sounding correctly when played above or below the subject, and must be conceived, therefore, in invertible (double) counterpoint.<ref name = "oxfcomp" /><ref>"Invertible Counterpoint" ''The Oxford Companion to Music'', ed. Alison Latham (Oxford and New York: Oxford University Press, 2002) {{cite book |url=http://www.oxfordreference.com/views/ENTRY.html?subview=Main&entry=t114.e3465|title=Oxford Reference Online, subscription access|isbn=978-0-19-957903-7|access-date=2007-03-16|last1=Latham|first1=Alison|year=2011|publisher=Oxford University Press }}</ref>

In [[tonality|tonal]] music, invertible contrapuntal lines must be written according to certain rules, because several intervallic combinations, while acceptable in one orientation, are not permissible when inverted. As an example, perfect fifths are contrapuntally acceptable, while the inversion of a perfect fifth results in a perfect fourth, which, unlike the perfect fifth, is considered a dissonance, requiring proper preparation and resolution.<ref>{{Cite Grove |last=Drabkin |first=William |title=Invertible Counterpoint}}</ref> The countersubject, if sounding at the same time as the answer, is transposed to the pitch of the answer.<ref>{{harvnb|Gedalge|1964|p=61}}</ref> Each voice then responds with its own subject or answer, and further countersubjects or free counterpoint may be heard.

It is customary in the exposition to alternate entrances of the subject (S) with entrances of the answer (A). However, this order is occasionally varied. For example, the exposition from [[Johann Sebastian Bach|J.S. Bach's]] ''[[Well-Tempered Clavier|Well-Tempered Clavier, Book 1]]'' Fugue No. 1 in C Major, BWV 846 uses a SAAS (subject-answer-answer-subject) exposition. A brief [[codetta]] is often heard connecting the various statements of the subject and answer, smoothly connecting each and often facilitating the modulation between the tonic and the key of the answer. The codetta, like other parts of the exposition, may be reused throughout the remainder of the fugue.<ref>{{harvnb|Gedalge|1964|pp=71–72}}</ref>

The first answer must occur as soon after the initial statement of the subject as possible; therefore, the first codetta is often absent or very short. In the example shown above of J.S. Bach's [[Prelude and Fugue in G minor, BWV 861|Fugue No. 16 in G minor, BWV 861]], the first codetta is absent. The subject concludes on the [[quarter note]] (or crotchet) B{{music|flat}} of the third beat of the second bar, which harmonizes the opening G of the tonal answer. The later codettas may be considerably longer, and often serve to develop the material heard in the subject/answer and countersubject and possibly introduce ideas heard in the second countersubject or free counterpoint that follows. They may also be present to delay, and therefore heighten the impact of, the reentry of the subject in another voice. Finally, they may be modulatory passages to return the fugue to the tonic.<ref>Paul Walker, "Fugue, §1: A Classic Fugue Analysed" {{cite web |url=http://www.grovemusic.com/shared/views/article.html?section=music.51678.1 |title=Grove Music Online |website=www.grovemusic.com |access-date=2007-02-18}}</ref>

The exposition usually concludes when all voices have given a statement of the subject or answer. In some fugues, especially those with an odd number of voices, the exposition will end with a redundant entry, or an extra presentation of the theme in a voice which has already entered.<ref name="oxfcomp" /> Furthermore, the entry of one of the voices may not be heard until considerably later. For example, in J.S. Bach's Fugue in C minor for Organ, BWV 549, the subject entrance in the lowest voice (played by the organ pedals), is not heard until near the end of the fugue.