Editing Leading tone (section)

=== Function ===
The leading-tone triad is used in several functions. It is commonly used as a [[passing chord]] between a [[root position]] tonic triad and a first inversion tonic triad:{{sfn|Forte|1979|loc=122}} that is, "In addition to its basic function of passing between I and I{{sup|6}}, VII{{sup|6}} has another important function: it can form a neighboring chord to I or I{{sup|6}}."{{sfn|Aldwell, Schachter, and Cadwallader|2010|loc=138}} In that instance, the leading-tone triad prolongs tonic through neighbor and passing motion. The example below shows two measures from the fourth movement of [[Ludwig van Beethoven|Beethoven]]'s [[Piano Sonata No. 3 (Beethoven)|Piano Sonata No. 3 in C major, Op. 2]]{{sfn|Forte|1979|loc=169}} in which a leading-tone triad functions as a passing chord between I and I{{sup|6}}.

:<score sound="1">
   \new PianoStaff <<
      \new Staff <<
         \new Voice \relative c'' {
             \stemUp \clef treble \key f \major \time 6/8
             a4. g f
             }
         \new Voice \relative c' {
             \stemDown
              <c f>4. <bes e> <a c>
              }
            >>
     \new Staff <<
         \new Voice \relative c,, {
             \clef "bass_8" \key f \major \time 6/8
             <f f'>4. <g g'> <a a'>
             }
         >>
    >>
</score>

The leading-tone triad may also be regarded as an incomplete [[dominant seventh chord]]: "A chord is called 'Incomplete' when its root is omitted. This omission occurs, occasionally, in the chord of the dom.-seventh, and the result is a triad upon the leading tone."{{sfn|Goetschius|1917|loc=72, §162–163, 165}}

:<score lang="lilypond">
{
\override Score.TimeSignature
#'stencil = ##f
\override Score.SpacingSpanner.strict-note-spacing = ##t
\set Score.proportionalNotationDuration = #(ly:make-moment 1/4)
\time 4/4 
\relative c'' { 
      <b d f>1^\markup { \column { "Leading-" "tone triad" } }
   <g b d f>^\markup { \column { "Dominant" "seventh chord" } }
   }
}
</score>
{{Image frame|content=<score>
   \new PianoStaff <<
      \new Staff <<
         \new Voice \relative c'' {
             \stemUp \clef treble \key d \major \time 4/4
             a4 a b cis d d cis\fermata
             }
         \new Voice \relative c' {
             \stemDown
              <d fis>4 <d fis> <d g> <e g> <fis a> <d gis> <e a>
              }
            >>
     \new Staff <<
         \relative c {
             \clef bass \key d \major \time 4/4
             d4 d g e d b a
             }
         >>
    >>
</score>|width=300|caption=A leading-tone triad (beat 4) and [[Secondary leading-tone chord|secondary leading-tone triad]] (beat 6) in the first phrase of the [[Bach chorale]] "Gott der Vater, wohn' uns bei" (slightly simplified){{sfn|Forte|1979|loc=122}}[[File:Leading-tone triad and secondary leading-tone triad in Chorale Gotte der Vater, wohn' uns bei.mid]]}}

Some sources say the chord is not a chord; some argue it is an incomplete dominant seventh chord, especially when the diminished triad is written in its first inversion (resembling a [[second inversion]] dominant seventh without a root):{{sfn|Herbert|1897|loc=102}}
{{Quote|The subtonic [i.e. leading-tone] chord is a very common chord and a useful one. The triad differs in formation from the preceding six [major and minor diatonic] triads. It is dissonant and active... a diminished triad. The subtonic chord belongs to the dominant family. The factors of the triad are the same tones as the three upper factors of the dominant seventh chord and progress in the same manner. These facts have led many theorists to call this triad a 'dominant seventh chord without root.'... The subtonic chord in both modes has suffered much criticism from theorists although it has been and is being used by masters. It is criticized as being 'overworked', and that much can be accomplished with it with a minimum of technique.{{sfn|Gardner|1918|loc=48, 50}}|sign=|source=}}
For example, vii{{music|dim}}{{sup|6}} often substitutes for V{{music|43 chord}}, which it closely resembles, and its use may be required in situations by [[voice leading]]: "In a strict four-voice texture, if the bass is doubled by the soprano, the VII{{sup|6}} [vii{{music|dim}}{{sup|6}}] is required as a substitute for the V{{music|43 chord}}".{{sfn|Forte|1979|loc=168}}