Editing Perfect fourth (section)

===20th century music===

====Western classical music====
{{Main|quartal and quintal harmony}}

[[Image:Ravel Ma Mere l'Oye Laideronnette.PNG|thumb|right|400px|Quartal harmony in "Laideronnette" from Ravel's Ma Mère l'Oye. The top line uses the [[pentatonic scale]]<ref>Bruce Benward and Marilyn Nadine Saker (2003). ''Music: In Theory and Practice, Vol. I'', seventh edition (Boston: McGraw-Hill): p.&nbsp;37. {{ISBN|978-0-07-294262-0}}.</ref> {{audio|Ravel Ma Mere l'Oye Laideronnette.mid|Play}}]]
In the 20th century, harmony explicitly built on fourths and fifths became important. This became known as quartal harmony for chords based on fourths and quintal harmony for chords based on fifths.
In the music of composers of early 20th century France, fourth chords became consolidated with [[ninth chord]]s, the [[whole tone scale]], the [[pentatonic]] scale, and [[polytonality]] as part of their language, and quartal harmony became an important means of expression in music by Debussy, [[Maurice Ravel]], and others.  Examples are found in Debussy's orchestral work ''[[La Mer (Debussy)|La Mer]]'' (The Sea) and in his piano works, in particular ''La cathédrale engloutie'' (The Sunken Cathedral) from his ''[[Préludes (Debussy)|Préludes]]'' for piano, ''Pour les quartes'' (For Fourths) and ''Pour les arpéges composées'' (For Composite Arpeggios) from his ''[[Études (Debussy)|Etudes]]''.

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|[[Image:Bartok's fourths.png|thumb|275px|center|Bartók's music, such as the ''String Quartet No. 2'', often makes use of a three-note basic cell, a perfect fourth associated with an external (C, F, G{{music|flat}}) or internal (C, E, F) minor second, as a common intervallic source in place of triadic harmonies.<ref name="Morgan">Robert P. Morgan (1991). ''Twentieth-Century Music: A History of Musical Style in Modern Europe and America'', The Norton Introduction to Music History (New York: W. W. Norton), pp.&nbsp;179–80. {{ISBN|978-0-393-95272-8}}.</ref>]]
|[[Image:Schoenberg's fourths.png|thumb|center|During Schoenberg's middle period he favoured a chord composed of two fourths, one perfect and one augmented (C, F, B or C, F{{music|sharp}}, B).<ref>Morgan (1991), p.&nbsp;71. "no doubt for its 'nontonal' quality"</ref><ref>{{Cite news|url=https://www.academia.edu/12232101|title=Introduction aux accords de quartes chez Arnold Schoenberg|last=Floirat|first=Bernard|year=2015|pages=19|website=www.academia.edu}}</ref>{{Failed verification|date=March 2016}}<!--This page contains only the last portion of a quotation in French translation from Schoenberg's Style and Idea. It says nothing at all about Schoenberg's middle period, or what sort of chord in fourths he favoured at that time.-->]]
|[[Image:Schoenberg string quartet quartal chord.png|thumb|150px|center|Quartal chord from Schoenberg's ''String Quartet No. 1'']]
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====Jazz====
Jazz uses quartal harmonies (usually called ''[[Voicing (music)|voicing]] in fourths'').

[[Cadence (music)|Cadences]] are often "altered" to include unresolved [[suspended chord]]s which include a fourth above the bass:

[[Image:II V I for wikipedia.png|thumb|none|275px|([[Image:Loudspeaker.svg|11px]][//upload.wikimedia.org/wikipedia/commons/b/b1/II_V9_I.MID Listen]) The II-V-I cadence ([[Image:Loudspeaker.svg|11px]][//upload.wikimedia.org/wikipedia/commons/6/6d/II_V9sus_I.MID Listen]) The fourth-suspension or "sus"-chord]]

[[Image:Maiden Voyage2.png|thumb|center|400px|Fourths in [[Herbie Hancock]]'s ''[[Maiden Voyage (composition)|Maiden Voyage]]''{{citation needed|date=January 2011}}]]

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|[[Image:Barretto Amor Artificial.png|thumb|right|345px|[[Image:Loudspeaker.svg|11px]] [//upload.wikimedia.org/wikipedia/commons/f/f4/Barretto_Amor_Artificial.mid Listen] The brass section of [[Ray Barretto]]'s version of ''Amor Artificial'']]
|[[Image:Nascimento Vera Cruz.png|thumb|right|345px|[[Image:Loudspeaker.svg|11px]] [//upload.wikimedia.org/wikipedia/commons/a/a3/Nascimento_Vera_Cruz.mid Listen] Guitar [[Break (music)|break]] from [[Milton Nascimento]]s composition "Vera Cruz"]]
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