Editing Perfect fourth (section)

===Classical and romantic===
The blossoming of tonality and the establishment of [[well temperament]] in Bach's time both had a continuing influence up to the late [[Romantic music|romantic]] period, and the tendencies towards quartal harmony were somewhat suppressed. An increasingly refined [[cadence (music)|cadence]], and triadic harmony defined the musical work of this era. Counterpoint was simplified to favour an upper line with a clear accompanying harmony. Still, there are many examples of dense counterpoint utilizing fourths in this style, commonly as part of the background urging the harmonic expression in a passage along to a climax.  [[Wolfgang Amadeus Mozart|Mozart]] in his so-called ''[[String Quartet No. 19 (Mozart)|Dissonance Quartet]]'' [[Köchel-Verzeichnis|KV]] 465 ([[Image:Loudspeaker.svg|11px]][//upload.wikimedia.org/wikipedia/commons/a/ab/Mozart_KV_465_1_Quarten_for_wikipedia.mid Listen]) used [[chromatic]] and [[whole tone]] scales to outline fourths, and the subject of the fugue in the third movement of [[Ludwig van Beethoven|Beethoven's]] ''[[Piano Sonata No. 31 (Beethoven)|Piano sonata op.&nbsp;110]]'' ([[Image:Loudspeaker.svg|11px]][//upload.wikimedia.org/wikipedia/commons/8/84/Beethoven_110_4_Quarten_for_wikipedia.mid Listen]) opens with three ascending fourths.  These are all melodic examples, however, and the underlying harmony is built on thirds.

Composers started to reassess the quality of the fourth as a consonance rather than a dissonance.  This would later influence the development of [[quartal and quintal harmony]].

The ''Tristan chord'' is made up of the [[Musical note|note]]s F{{music|natural}}, B{{music|natural}}, D{{music|sharp}} and G{{music|sharp}} and is the first chord heard in [[Richard Wagner]]'s [[opera]] ''[[Tristan und Isolde]]''.

: <score lang="lilypond" override_ogg="Wagner Tristan opening (orchestral).ogg">
    {
      \new PianoStaff <<
        \new Staff <<
            \new Voice \relative c'' {
                \clef treble \key a \minor \time 6/8
                \voiceOne \partial8 r8 R2. \once \override NoteHead.color = #red gis4.->(~ gis4 a8 ais8-> b4~ b8) r r
                }
            \new Voice \relative c' {
                \override DynamicLineSpanner.staff-padding = #4.5
                \once \override DynamicText.X-offset = #-5
                \voiceTwo \partial8 a\pp( f'4.~\< f4 e8 \once \override NoteHead.color = #red dis2.)(\> d!4.)~\p d8 r r
                }
            >>
        \new Staff <<
            \relative c {
                \clef bass \key a \minor \time 6/8
                \partial8 r8 R2. \once \override NoteHead.color = #red <f b>2.( <e gis>4.)~ <e gis>8 r r
                }
            >>
    >> }
</score>

The chord had been found in earlier works, notably [[Ludwig van Beethoven|Beethoven]]'s [[Piano Sonata No. 18 (Beethoven)|Piano Sonata No. 18]], but Wagner's usage was significant, first because it is seen as moving away from traditional [[tonal harmony]] and even towards [[atonality]], and second because with this chord Wagner actually provoked the ''sound'' or structure of musical harmony to become more predominant than its ''function'', a notion which was soon after to be explored by Debussy and others.

[[Image:Baby Yaga for wikipedia.png|thumb|right|400px|Measures 24 to 27 from Mussorgsky's ''The Hut on Fowl's Legs'']]

Fourth-based harmony became important in the work of Slavic and Scandinavian composers such as [[Modest Mussorgsky]], [[Leoš Janáček]], and [[Jean Sibelius]]. These composers used this harmony in a pungent, uncovered, almost archaic way, often incorporating the [[folk music]] of their particular homelands. Sibelius' ''Piano Sonata in F-Major op.&nbsp;12'' of 1893 used [[tremolo]] passages of near-[[quartal harmony]] in a way that was relatively difficult and modern. Even in the example from Mussorgsky's piano-cycle ''[[Pictures at an Exhibition]]'' ''(Избушка на курьих ножках (Баба-Яга) – The Hut on Fowl's Legs)'' ([[Image:Loudspeaker.svg|11px]][//upload.wikimedia.org/wikipedia/commons/2/29/Baba_Yaga_Quarten_for_wikipedia.mid Listen]) the fourth always makes an "unvarnished" entrance.

The romantic composers [[Frédéric Chopin]] and [[Franz Liszt]], had used the special "thinned out" sound of fourth-chord in late works for piano (''[[Nuages Gris|Nuages gris]]'' (Grey Clouds), ''La lugubre gondola'' (The Mournful Gondola), and other works).

In the 1897 work ''[[The Sorcerer's Apprentice (Dukas)|The Sorcerer's Apprentice]] (L'Apprenti sorcier)'' by [[Paul Dukas]], the repetition of rising fourths is a musical representation of the tireless work of out-of-control walking brooms causes the water level in the house to "rise and rise". Quartal harmony in Ravel's ''[[Sonatine (Ravel)|Sonatine]]'' and ''[[Ma Mère l'Oye]]'' (Mother Goose) would follow a few years later.