Editing Diminished triad (section)

==Harmonic function==
{{Image frame|content=<score sound="1" override_midi="Bach - WTC I, Prelude in G Major diminished chord.mid">
    {
      #(set-global-staff-size 14)
      \override Score.SpacingSpanner.strict-note-spacing = ##t
      \set Score.proportionalNotationDuration = #(ly:make-moment 1/2)
      \new PianoStaff <<
        \new Staff <<
            \relative c'' {
                \key g \major \time 24/16
                g16 b d g d b d b g b g d  
                e g c e c g c g e g e c  
                a c fis a fis c fis c a c a fis  
                g b d g d b d b g b g d
                }
            >>
        \new Staff <<
            \relative c' {
                \clef F \key g \major \time 24/16
                g8.[_\markup { \concat { "I" \hspace #20.5 "IV" \hspace #19.5 "vii" \raise #1 \small  "o" \hspace #19.5 "I" } }
                g,] r g' g[ g,] r g' g[ g,] r g' g[ g,] r g'
                }
            >>
    >> }
</score>|caption=A diminished triad substituting for dominant chord in [[Johann Sebastian Bach|J. S. Bach's]] ''[[Well-Tempered Clavier]]'' I, Prelude in G major.<ref>{{cite book|title=Das Wesen des musikalischen Kunstwerks: Eine Einführung in Die Lehre Heinrich Schenkers|last=Jonas|first=Oswald|date=1982|isbn=0-582-28227-6|page=[https://archive.org/details/introductiontoth0000jona/page/25 25]|publisher=Longman |translator-last=Rothgeb|translator-first=John|trans-title=Introduction to the Theory of [[Heinrich Schenker]]|author-link=Oswald Jonas|orig-year=1934|url=https://archive.org/details/introductiontoth0000jona/page/25}}</ref>}}

In [[Major scale|major scales]], a diminished triad occurs only on the seventh [[Degree (music)|scale degree]]. For instance, in the key of C, this is a B diminished triad (B, D, F). Since the triad is built on the seventh scale degree, it is also called the ''[[Leading-tone#Leading-tone triad|leading-tone triad]]''.  This chord has a [[dominant function]]. Unlike the [[dominant triad]] or [[Dominant seventh chord|dominant seventh]], the leading-tone triad functions as a [[prolongation]]al chord rather than a structural chord since the strong root motion by fifth is absent.{{sfn|Roig-Francolí|2011|page=248}}

On the other hand, in [[Natural minor scale|natural minor scales]], the diminished triad occurs on the second scale degree; in the key of C minor, this is the D diminished triad (D, F, A{{music|b}}). This triad is consequently called the ''[[supertonic]] diminished triad''. Like the supertonic minor triad found in a major key, the supertonic diminished triad has a [[Predominant chord|predominant function]], almost always resolving to a dominant functioning chord.{{sfn|Roig-Francolí|2011|page=174}}

If the music is in a minor key, diminished triads can also be found on the raised seventh note, {{music|#}}vii{{music|dim}}. This is because the [[ascending melodic minor scale]] has a raised sixth and seventh degree. For example, the chord progression {{music|#}}vii{{music|dim}}–i is common.

The leading-tone diminished triad and supertonic diminished triad are usually found in [[first inversion]] (vii{{music|dim}}<sup>6</sup>  and ii{{music|dim}}<sup>6</sup>, respectively) since the spelling of the chord forms a diminished fifth with the bass.{{sfn|Roig-Francolí|2011|page=248}} This differs from the [[fully diminished seventh chord]], which commonly occurs in [[root position]].<ref name="B&S2">{{cite book|title=Music in Theory and Practice: Volume II|last1=Benward|last2=Saker|date=2009|isbn=978-0-07-310188-0|edition=8th|page=76|publisher=McGraw-Hill }}</ref> In both cases, the bass resolves up and the upper voices move downwards in [[contrary motion]].<ref name="B&S2" />