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{{Short description|A major triad plus the harmonic seventh interval}}
[[File:Harmonic seventh chord on C.png|thumb|right|"[[Quarter tone#Interval size in equal temperament|Tempered]] harmonic seventh" chord on C with the 7th at 950 [[Cent (music)|cents]] above C. {{audio|Harmonic seventh chord on C.mid|Play}} See: [[flat (music)|three-quarter flat]].]]
[[File:Harmonic seventh chord just on C.png|thumb|right|Just harmonic seventh chord on C with the 7th 968.826 cents above C, a [[septimal quarter tone]] lower than B{{music|b}}. {{audio|Harmonic seventh chord just on C.mid|Play just}}]]
[[File:Dominant seventh chord on C.png|thumb|right|Dominant seventh chord on C, C<sup>7</sup>, with the 7th 1000 cents above C. See [[flat (music)|flat]]. {{audio|Dominant seventh chord on C.mid|Play}}]]

The '''harmonic seventh chord''' is a [[major chord|major triad]] plus the [[harmonic seventh]] interval (ratio of 7:4, about 968.826 [[cent (music)|cents]]<ref name="Bosanquet">Bosanquet, Robert Holford Macdowall (1876). ''An elementary treatise on musical intervals and temperament'', pp. 41-42. Diapason Press; Houten, The Netherlands. {{ISBN|90-70907-12-7}}.</ref>). This [[interval (music)|interval]] is somewhat narrower (about 48.77 cents flatter, a [[septimal quarter tone]]) and is "sweeter in quality" than an "ordinary"<ref name="Novel">"On Certain Novel Aspects of Harmony", p.119. Eustace J. Breakspeare. ''Proceedings of the Musical Association'', 13th Sess., (1886–1887), pp. 113–131. Published by: Oxford University Press on behalf of the Royal Musical Association.</ref> [[minor seventh]], which has a [[just intonation]] ratio of 9:5<ref>"The Heritage of Greece in Music", p.89. Wilfrid Perrett. ''Proceedings of the Musical Association'', 58th Sess., (1931–1932), pp. 85–103. Published by: Oxford University Press on behalf of the Royal Musical Association.</ref> (1017.596 cents), or an [[equal temperament|equal-temperament]] ratio of 1000 cents (2<sup>{{frac|5|6}}</sup>:1).

==Uses==

Since [[barbershop music]] tends to be sung in [[just intonation]], the barbershop seventh chord may be accurately termed a harmonic seventh chord. As guitars, pianos, and other equal-temperament instruments cannot play this chord, it is frequently approximated by a [[dominant seventh chord]].  A frequently encountered example of the harmonic seventh chord is the last word of the "...&nbsp;and many more!" modern addition (which is formally referred to as a [[Tag (barbershop music)|tag]]) to the song "[[Happy Birthday to You]]" When sung by professional singers, the harmony on the word "more" typically takes the form of a harmonic seventh chord.<ref name="Mathieu pg. 126">{{cite book |last=Mathieu |first=W.A. |year=1997 |title=Harmonic Experience |publisher=Inner Traditions International |place=Rochester, VT |ISBN=0-89281-560-4 |page=126 }}</ref>
The use of dominant seventh chords in blues may be an approximation of an older practice of using harmonic seventh chords.<ref>{{cite AV media |title=The world's most important chord progression |medium=video |via=[[YouTube]] |url=https://www.youtube.com/watch?v=5y4T9SkNYFo }}</ref>

Wendy Carlos's [[alpha scale]] has, "excellent harmonic seventh chords ... using the inversion of 7:4, i.e. {{small|{{sfrac| 8 | 7 }}}}" (a [[septimal whole tone]]).<ref>{{cite web |last=Carlos |first=Wendy |author-link=Wendy Carlos |date=1989–1996 |title=Three asymmetric divisions of the octave |website=WendyCarlos.com |url=http://www.wendycarlos.com/resources/pitch.html }}</ref> {{audio|Alpha scale harmonic seventh chord on C.mid|Play}}.

It is suggested that the harmonic seventh on the dominant not be used as a [[suspension (music)|suspension]], since this would create a mistuned fourth over the tonic.<ref>{{cite book |first1=Robert |last1=Halford |first2=MacDowall |last2=Bosanquet |first3=Rudolf |last3=Rasch |year=1876 |title=An Elementary Treatise on Musical Intervals and Temperament |place=London, UK |publisher=MacMillan |page=[https://archive.org/details/imslp-elementary-treatise-on-musical-intervals-and-temperament-bosanquet-robert-/page/n58/mode/1up 41]–42 |url=https://archive.org/details/imslp-elementary-treatise-on-musical-intervals-and-temperament-bosanquet-robert- }}</ref> The harmonic seventh of G, F{{music|7}}{{music|+}}, is lower than the perfect fourth over C, F{{music|natural}}, by [[Archytas' comma]] (27.25&nbsp;cents). [[22 equal temperament]] avoids this problem because it tempers out this comma, while still offering a reasonably good approximation of the harmonic seventh chord.

==Barbershop seventh==
[[File:Barbershop secondary dominant.png|thumb|Successive seventh chords starting with a secondary dominant: V<sup>7</sup>/V (II<sup>7</sup>)–V<sup>7</sup>–I, in this case G<sup>7</sup>–C<sup>7</sup>–F). Note the chromatic voice leading (B{{music|natural}}–B{{music|b}}–A), and that the F in the first chord is [[Archytas' comma|27.26&nbsp;cents]] lower than the F in the third chord. {{audio|Barbershop secondary dominant.mid|Play}}]]

{{quote|''barbershop seventh chord''. A chord consisting of the root, third, fifth, and flatted seventh degrees of the scale. It is characteristic of barbershop arrangements. When used to lead to a chord whose root is a fifth below the root of the barbershop seventh chord, it is called a [[dominant seventh chord]]. Barbershoppers sometimes refer to this as the 'meat 'n' taters chord'. In the nineteenth and early twentieth centuries, these chords were sometimes called 'minors'. [as in minor ''seventh chord'']"|Averill 2003<ref>{{cite book |last=Averill |first=Gage |year=2003 |title=Four Parts, No Waiting: A social history of American barbershop harmony |page=205 |ISBN=0-19-511672-0 }}</ref>}}

The '''barbershop seventh''' is the name commonly given by practitioners of [[barbershop music]] to the seventh of and the major-minor seventh or dominant [[Seventh chord#Types of seventh chords|seventh chord]], when it is used in a [[Barbershop arranging|barbershop arrangement]] or performance. "Society arrangers believe that a song should contain anywhere from 35–60&nbsp;percent dominant seventh chords to sound 'barbershop'—and when they do, barbershoppers speak of being in 'seventh heaven.'"{{sfnp|Averill|2003|p=163}}

Barbershop music features both major-minor seventh chords with dominant function (resolving down a perfect fifth), often in chains ([[secondary dominant]]s), and nondominant major-minor seventh chords.<ref>{{cite book |last=McNeil |first=W.K. |year=2005 |title=Encyclopedia of American Gospel Music |page=26 |ISBN=9780415941792 }}</ref>

Beginning in the 1940s, barbershop revival singers "have self-consciously tuned their dominant seventh and tonic chord in [[just intonation]] to maximize the overlap of common tones, resulting in a ringing sound rich in harmonics" called 'extended sound', 'expanded sound', 'fortified sound', "the voice of the angels".<ref name=Averill-2003-p164>{{harvp|Averill|2003|p=164}}</ref> The first positive mention of such practice appears to be by {{harvp|Reagan|1944}}.<ref>{{cite magazine |last=Reagan |first='Molly' |year=1944 |title=Mechanics of barbershop harmony |magazine=Harmonizer}}</ref> The example of a dominant chord tuned to 100, 125, 150, and 175&nbsp;[[Hertz (unit)|Hz]], or the 4th, 5th, 6th, and 7th harmonics of a 25&nbsp;Hz fundamental is given,<ref name=Averill-2003-p164/> making the seventh of the chord a "harmonic seventh".

{{quote|There's a chord in a barbershop that makes the nerve ends {{nobr|tingle ... .}} We might call our chord a Super-Seventh! ... The notes of our chord have the exact frequency ratios 4–5–6–7. With these ratios, overtones reinforce overtones. There's a minimum of dissonance and a distinctive ringing sound. How can you detect this chord? It's easy: You can't mistake it, for the signs are clear; the overtones will ring in your ears; you'll experience a spinal shiver; bumps will stand out on your arms; you'll rise a trifle in your seat.| Art Merill (1951)<ref>{{cite magazine |last=Merrill |first=Art |year=1951 |title=You can call off the search — for we've found the lost chord |magazine=Harmonizer |volume=10 |issue=3 |page=27 }} Cited in {{harvp|Averill|2003|p=164}}.</ref><ref name=Averill-2003-p164/>}}

It is normally voiced with the lowest note (the bass) on a root or a fifth, and its [[close harmony]] sound is one of the hallmarks of barbershop music.

When tuned in [[just intonation]] (as in barbershop singing), this chord is called a ''harmonic seventh chord''.

==Comparison with equal temperament==

[[File:Barbersharp 12TET and 4-5-6-7 audacity.png|thumb|right|450px|Equal tempered and just renditions of the harmonic seventh chord starting at 400 Hz. The audio file alternates between 12-TET and just, beginning with 12-TET: {{audio|Barbersharp 12TET and 4-5-6-7 natural.ogg|Play}}]]

[[Audacity (audio editor)|Audacity]] can be used to render [[Musical tone#Pure tone|pure tone]] versions of the harmonic seventh with both equal-tempered and just tuning.  These signals can also be graphed in order to illustrate the more complex pattern associated with the equal tempered scale.  Both chords are based on a pitch of 400&nbsp;Hz, with the just pitches at 500, 600, and 700&nbsp;Hz.

The figure also shows the discrepancy between the just scale in comparison to the equal-tempered scale (in [[Cent (music)|cents]]).  For example, the just tone at 500&nbsp;Hz is [[flat (music)|flatter]] than 503.2&nbsp;Hz by 13.69 cents.  Also, the 600&nbsp;Hz tone is [[Sharp (music)|sharp]] by 1.955 cents, and the 700&nbsp;Hz tone is flat by 31.17 cents.

{| class="wikitable" style="text-align: center;"
|+ Comparison of dominant seventh and harmonic seventh chords
|-
! Tuning !! Dominant seventh !! Harmonic seventh
|-
| Just intonation || &nbsp; || [[File:Harmonic seventh chord just intonation.wav]]
|-
| 12-TET (72-TET) || [[File:Dominant seventh chord in 12-EDO.wav]] || [[File:Quasi-tempered harmonic seventh chord in 72-EDO.wav]]
|-
| 19-TET || [[File:Dominant seventh chord in 19-EDO.wav]] || [[File:Harmonic (subminor) seventh chord in 19-EDO.wav]]
|-
| 31-TET || [[File:Dominant seventh chord in 31-EDO.wav]] || [[File:Harmonic seventh chord in 31-EDO.wav]]
|-
| 43-TET || [[File:Dominant seventh chord in 43-EDO.wav]] || [[File:Harmonic seventh chord in 43-EDO.wav]]
|}

==References==
{{reflist|25em}}

==External links==
* [https://www.youtube.com/watch?v=F5bYnRkwpco Play that barbershop chord] (YouTube video)

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[[Category:Barbershop music]]
[[Category:Seventh chords]]