Editing Blues (section)

==Form==
The blues form is a [[cyclic form|cyclic musical form]] in which a repeating [[chord progression|progression of chords]] mirrors the [[call and response (music)|call and response]] scheme commonly found in African and African-American music. During the first decades of the 20th century blues music was not clearly defined in terms of a particular chord progression.<ref>{{cite web|title=The Evolution of the 12-Bar Blues Progression|url=http://www.bobbrozman.com/tip_evol12bar.html|author=Brozman, Bob|author-link=Bob Brozman|year=2002|access-date=May 2, 2009|archive-date=May 25, 2010|archive-url=https://web.archive.org/web/20100525222458/http://www.bobbrozman.com/tip_evol12bar.html|url-status=dead}}</ref> With the popularity of early performers, such as [[Bessie Smith]], use of the [[twelve-bar blues]] spread across the music industry during the 1920s and 1930s.<ref>[[Samuel Charters|Charters, Samuel]]. In ''Nothing but the Blues''. p. 20</ref> Other chord progressions, such as [[8-bar blues|8-bar]] forms, are still considered blues; examples include "[[How Long, How Long Blues|How Long Blues]]", "[[Trouble in Mind (song)|Trouble in Mind]]", and [[Big Bill Broonzy]]'s "[[Key to the Highway]]". There are also [[16-bar blues]], such as [[Ray Charles]]'s instrumental "Sweet 16 Bars" and [[Herbie Hancock]]'s "[[Watermelon Man (composition)|Watermelon Man]]". Idiosyncratic numbers of bars are occasionally used, such as the 9-bar progression in "[[Sitting on Top of the World]]", by [[Walter Vinson]].

{|class="wikitable floatright"
|style="width:200px; text-align:center;"|Chords played over a 12-bar scheme:
|style="width:200px; text-align:center;"|Chords for a blues in C:
|-
|align=center|
{| class="wikitable"
|- style="text-align:center;"
|style="width:50px;"|I
|style="width:50px;"|I or IV
|style="width:50px;"|I
|style="width:50px;"|I7
|- style="text-align:center;"
|style="width:50px;"|IV
|style="width:50px;"|IV
|style="width:50px;"|I
|style="width:50px;"|I7
|- style="text-align:center;"
|style="width:50px;"|V
|style="width:50px;"|V or IV
|style="width:50px;"|I
|style="width:50px;"|I or V
|}
|align=center|
{|class="wikitable"
|- style="text-align:center;"
|style="width:50px;"|C
|style="width:50px;"|C
|style="width:50px;"|C
|style="width:50px;"|C7
|- style="text-align:center;"
|style="width:50px;"|F
|style="width:50px;"|F
|style="width:50px;"|C
|style="width:50px;"|C7
|- style="text-align:center;"
|style="width:50px;"|G
|style="width:50px;"|G
|style="width:50px;"|C
|style="width:50px;"|C
|}
|}

The basic 12-bar lyric framework of many blues compositions is reflected by a standard harmonic progression of 12 bars in a [[Time signature|4/4 time signature]]. The blues [[Chord (music)|chords]] associated to a [[twelve-bar blues]] are typically a set of three different chords played over a 12-bar scheme. They are labeled by [[Roman number]]s referring to the [[degree (music)|degrees]] of the progression. For instance, for a blues in the [[key (music)|key]] of C, C is the [[tonic chord]] (I) and F is the [[subdominant chord|subdominant]] (IV).

The last chord is the [[dominant chord|dominant]] (V) [[turnaround (music)|turnaround]], marking the transition to the beginning of the next progression. The lyrics generally end on the last beat of the tenth bar or the first beat of the 11th bar, and the final two bars are given to the instrumentalist as a break; the harmony of this two-bar break, the turnaround, can be extremely complex, sometimes consisting of single notes that defy analysis in terms of chords.

Much of the time, some or all of these chords are played in the [[harmonic seventh]] (7th) form. The use of the harmonic seventh interval is characteristic of blues and is popularly called the "blues seven".<ref>{{cite web|author=Fullman, Ellen|title=The Long String Instrument|work= MusicWorks| publisher= Issue 37, Fall 1987 |url=http://www.deepmedia.org/ellenfullman/mw85/fullman_article.pdf |url-status=dead |archive-url=https://web.archive.org/web/20080625045305/http://www.deepmedia.org/ellenfullman/mw85/fullman_article.pdf |archive-date=June 25, 2008}}</ref> Blues seven chords add to the harmonic chord a note with a frequency in a 7:4 ratio to the fundamental note. At a 7:4 ratio, it is not close to any interval on the conventional Western [[diatonic scale]].<ref>{{cite web|title=A Jazz Improvisation Almanac, Outside Shore Music Online School|url=http://www.outsideshore.com/school/music/almanac/html/Music_Theory/Jazz_Scales/Blues_And_Bebop_Scales/Blues_Scale.htm|url-status=dead|archive-url=https://archive.today/20120911011306/http://www.outsideshore.com/school/music/almanac/html/Music_Theory/Jazz_Scales/Blues_And_Bebop_Scales/Blues_Scale.htm|archive-date=September 11, 2012}}</ref> For convenience or by necessity it is often approximated by a [[minor seventh]] interval or a [[dominant seventh chord]].

[[File:A minor pentatonic scale.svg|thumb|upright=1.6|A minor [[pentatonic scale]]; {{Audio|PentMinor.mid|play}}]]

In [[melody]], blues is distinguished by the use of the [[Flat (music)|flattened]] [[major third|third]], [[tritone|fifth]] and [[minor seventh|seventh]] of the associated [[major scale]].<ref>Ewen, p. 143</ref>

Blues [[shuffle note|shuffles]] or [[walking bass]] reinforce the trance-like rhythm and call-and-response, and they form a repetitive effect called a [[groove (popular music)|groove]]. Characteristic of the blues since its Afro-American origins, the shuffles played a central role in [[swing music]].<ref>Kunzler, p. 1065</ref> The simplest shuffles, which were the clearest signature of the [[Rhythm and blues|R&B]] wave that started in the mid-1940s,<ref>Pearson, Barry. In ''Nothing but the Blues''. p. 316</ref> were a three-note [[riff]] on the bass strings of the guitar. When this riff was played over the bass and the drums, the [[Groove (music)|groove]] "feel" was created. Shuffle rhythm is often vocalized as "''dow'', da ''dow'', da ''dow'', da" or "''dump'', da ''dump'', da ''dump'', da":<ref>Hamburger, David (2001). ''Acoustic Guitar Slide Basics''. {{ISBN|978-1-890490-38-6}}</ref> it consists of uneven, or "swung", eighth notes. On a guitar this may be played as a simple steady bass or it may add to that stepwise quarter note motion from the fifth to the sixth of the chord and back.