Editing Augmented sixth chord (section)

===Italian sixth===
{{Image frame|content=<score sound="1" override_midi="BeethovenOp78.mid">
    {
      \new PianoStaff <<
        \new Staff <<
            \relative c' {
                \tempo "Allegro vivace"
                \clef treble \key fis \major \time 2/4
                \override DynamicLineSpanner.staff-padding = #2.8
                <fis bis>4.(\f <eis cis'>8)
                <eis gis> r r <fis ais>\p
                <dis b'!>8.( <cis ais'>16) <b gis'>8-. <ais fis'>-.
                <gis eis'>4 r
                }
            >>
        \new Staff <<
            \relative c {
                \clef bass \key fis \major \time 2/4
                <d fis>4.( <cis gis'>8)
                <b! cis> r r ais
                gis8.( ais16) b8-. bis-.
                cis4 r
                }
            >>
    >> }
</score>|width=420|caption=The second movement of [[Beethoven]]'s [[Piano Sonata No. 24 (Beethoven)|Piano Sonata in F{{music|sharp}} major, Op. 78]], begins with an Italian sixth chord.}}
The Italian sixth (It<sup>+6</sup> or It<sup>6</sup> or {{music|sharp}}iv<sup>6</sup>) is derived from iv<sup>6</sup> with an altered fourth [[Scale-degree|scale degree]], {{music|sharp}}{{music|scale|4}}. This is the only augmented sixth chord comprising just three distinct notes; in [[Four-part harmony|four-part writing]], the tonic pitch is [[Voicing (music)#Doubling|doubled]]<!--wouldn't it be because it's the best voice leading strategy?-->.
{{block indent|<score sound="1">
    {
      \new PianoStaff <<
        \new Staff <<
            \relative c' {
                \clef treble \key c \major \time 4/4
                <c fis>1 <d g>
                }
            >>
        \new Staff <<
            \relative c' {
                \clef bass \key c \major \time 4/4
                <aes c>1_\markup { \concat { "It" \raise #1 \small "+6" \hspace #4.3 "V" } } 
                <g b> \bar "||"
                }
            >>
    >> }
</score>}}

The Italian sixth is enharmonically equivalent to an incomplete [[dominant seventh]].{{sfn|Rimsky-Korsakov|1924|p=121}} {{music|b}}VI7={{music|#}}V7: A{{music|b}}, C, (E{{music|b}},) G{{music|b}}.