CIR­CLE OF FOURTHS The Es­sen­tial Sys­tem

Si­mon Troup ex­plains how the Cy­cle of 4ths is a pow­er­ful song­writ­ing tool and also a great chord pro­grs­sion for im­pro­vis­ing over.

Guitar Techniques - - Guitar Techniques -

The cir­cle of 4ths is a vari­a­tion on a con­cept known as the cir­cle of 5ths. These conepts are closely re­lated since a 4th is es­sen­tially an in­verted 5th; but the cir­cle of 4ths cre­ates a spe­cific style of com­po­si­tion, and it’s this that we are fo­cus­ing on here.

The ‘cir­cle’ is the vis­ual rep­re­sen­ta­tion of a pro­gres­sion of di­a­tonic chords that can be heard in nu­mer­ous styles of mu­sic. Good mu­si­cians recog­nise these pat­terns just as they recog­nise a 12-bar blues. Know­ing how to han­dle such changes, and to em­bel­lish and im­pro­vise over them, is nec­es­sary if you want to be a ver­sa­tile mu­si­cian. You’ll find these pro­gres­sions in the mu­sic of Bach, Bacharach and The Bea­tles, and as easy to find in jazz as in Ju­das Priest songs - which should tell you some­thing about their uni­ver­sal ap­peal.

The build­ing blocks of these pro­gres­sions are the di­a­tonic chord fam­i­lies of the ma­jor and mi­nor scales - ie sets of chords built us­ing scale tones only - as ei­ther tri­ads or 7th chords. Most people’s first ex­pe­ri­ence of this is learn­ing the se­quence ‘ma­jor mi­nor mi­nor, ma­jor ma­jor mi­nor’, rep­re­sent­ing the pat­tern of chords in a ma­jor key, I through VIm. There­fore our first few ex­am­ples demon­strate dif­fer­ent ideas us­ing this har­monised chord scale.

The di­a­gram (Fig 1) op­po­site shows the di­a­tonic cir­cle of 4ths in the key of C (C D E F G A B) as a se­ries of 7th chords: Cmaj7-Fma­j7Bm7b5-Em7-Am7-Dm7-G7-Cmaj7. These are on the outer ring. The in­ner ring is a Ro­man nu­meral sys­tem from I to VII, the nu­mer­als tal­ly­ing with the outer cir­cle chords (I=Cmaj7, IV=Fmaj7 etc) and smaller nu­mer­als fill­ing in the gaps be­tween the 4th chords.

Once you have un­der­stood this di­a­gram, it is worth­while to do the same in other keys. At first you could fo­cus first on gui­tar friendly keys such as D ma­jor (D E F# G A B C#), G ma­jor (G A B C D E F#), A ma­jor (A B C# D E F# G#) and E ma­jor (E F# G# A B C# D#).

Fig 2 shows the di­a­tonic chord fam­ily of C ma­jor with each chord be­ing a 7th of some kind (maj7, m7, 7 and m7b5). Again, get to know the 7th chords in ev­ery key.

Fig 3 shows how sec­ondary dom­i­nants can be ap­plied to each chord in the ma­jor scale (here, C ma­jor). A sec­ondary dom­i­nant is a dom­i­nant 7th chord that re­solves to an­other chord in a scale other than the tonic (the C of C ma­jor), mak­ing a smooth tran­si­tion from one chord to an­other. While, say, Cmaj7-Dm7 is a great chord pro­gres­sion the Dm7 won’t sound re­solved un­til it’s pre­pared for prop­erly. By adding A7 in front of Dm (or Dm7) the change is more re­solved, as if you’ve moved away from C to be in Dm. Sec­ondary dom­i­nants can prove very use­ful in a cir­cle of 4ths sce­nario; Cmaj7-Fmaj7 can be elab­o­rated on with Cmaj7-C7-Fmaj7 (Fmaj7 sounds more set­tled now) or sim­i­larly, Am7-Dm7 can be en­hanced as Am7-A7-Dm7.

With these three di­a­grams un­der­stood (and ideally ex­plored by you, sooner or later), you’re now ready to tackle the ex­am­ples that fol­low. You’ll go from chord primers that har­monise the C ma­jor scale to play­ing chord pro­gres­sions in cir­cles of 4ths then onto us­ing sec­ondary dom­i­nants. Af­ter this, you’ll ex­plore the same ter­rain us­ing arpeg­gios. Happy cir­cling!

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