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Fuzzy Logic Jazz Theorems



Jazz can be a nightmare for those with a rudimentary knowledge of classical music theory. Somethings just won't make sense. Don't worry.. Many classical standards from Bizet's Carmen to Rimsky-Korsakov's Flight of the Bumblebee resplendent with chromaticism also fly in the face of Diatonic structures used to teach the principles

Some theorems apply in some circumstances while fail in other. As a classic example. In the earliest era of jazz "swing" was accomplished via poly rhythms not the triplets / shuffle pattern we used today. It was a two over three beat. A march (2/4) and a Waltz (3/4) both played at the same time..

There are two approaches to jazz performance. One where everything is exactly notated and arranged for performance and generally intended for Big Band settings and the other where by choices are made by the player using both conventional and non conventional choices for interpretation.

Without further adieu things to consider about jazz as you study it, perform it, and generally get the hang of it.

In Jazz -

  • The Dominant 7th chord refers not to it's function as the 5th (V) chord but to the spelling of the Chord. That being a Major Chord with a flattened 7th degree. Dominant 7th chords are implicit while Major Seventh Chords are Explicit. As an example If a song is in the Key of C and you see a C7 it means the chord has a flattened 7th degree (C-E-G-Bb) However if the chord is Expressly written as a Maj7 it means it explicitly utilizes the major 7th degree (C-E-G-B )
  • A common substitutions where by a minor chord is converted to a dominant 7th. In popular form I-VI7-ii7-V7 progressions and turnarounds.
  • When expressing Jazz theory of chord movement is expressed in Roman Numeral based on scale degrees. Uppercase denotes Major while lower case denotes minor. I,ii,iii,IV,V,vi,
  • Chords that are not derived from the major scale degrees are expressed as flats bII, bIII, bV bVII, bVII In usage flat chords can be functional passing or neighboring chords to a target chord, or substitutions (tritone and more) or representations of chords based on minor keys degrees or operate as nonfunctional harmony or harmonic justification (block chords) or when the key is specifically a minor key.
  • Common relative major for minor or minor for major is not considered a valid substitution. One cannot simply supplant a IV chord for a ii chord or vice versa.
  • Extended chord names are derived from chord scale values Extending the scale unless explicitly expressed as a major 7th degree it is assumed to be dominant and assumed that the 7th value is present. For example D(7)9 D-F#-A-C-E C11 C-E-G-Bb-F G13 G-B-D-F-E
  • In practice the 5th is often omitted from chord voicings. and with jazz guitar where a 13th chord appears the third appears as the 10th. EG a G13 would be commonly voiced G-F-B-E or in the form of an inversion a G13 may be expressed as F-B-E-G. As the bass player is expected to hold down the root of the chord Guitarists and Keyboard players may opt for "rootless chords"
  • Tritone Substitution http://en.wikipedia.org/wiki/Tritone_substitution Can be used on any chord (not just the functioning V) Where a major chord is expressed as a dominant (1-3-5-b7) Although it is most commonly used as a subitution for the functioning V or I chord.
  • In expanded tritone substitution any chord that contains the original tritone (major 3rd,b7th) can be substituted with any chord that also contains those same intervals. EG C7 (C-E-G-Bb) Em7b5 (E-G-Bb-D)
  • In Jazz the full diminished chord is built of equal minor thirds values creating a diminished 6th (B-D-F-Ab) they are less common. More common is the Half Diminished. Because this chord rarely functions as the vii chord in a progression it is generally expressed as m7b5
  • Get used to that m7b5 chord you'll see it alot. It's commonly used as a substitute for Dominant 9 chords built on the 3rd interval. Example G-B-F-A becomes B-F-A-D. It's often used as substitution chord built on the 6th degree of a minor chord. Example Cm (C-Eb-G) becomes Amb7 (A-G-C-Eb) . The m7b5 is used as a bii substitution for the major7 chord. GM7 (G-B-D-F#) becomes Abm7b5 (Ab-B-D-Gb). Occasionally it is used as a "pivot" chord after a series of whole step modulations to return to the root (Bluesette) or simply as the diminished chord ala "Autumn Leaves"

If none of the above makes any sense from what you believe to be true...Well welcome to the world of Jazz, the art of the inexact. It's not intended as science and this barely covers the basics. Don't worry you are not expected to learn all this in a day or a week. Simply take note of it as you read it and then refer back to it as you develop. Not all these concepts are used all the time in jazz simply because something "Can" be done doesn't mean it by default "should" or "has to" be done And yet none of them can be fully comprehended until you've experienced them time and time again. Experience that comes from playing the principles, Not reading them, not listening to them in reflection but experiencing them in the moment.

Still want to play Jazz?

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  • When expressing Jazz theory of chord movement is expressed in Roman Numeral based on scale degrees. Uppercase denotes Major while lower case denotes minor. I,ii,iii,IV,V,vi,

I either misunderstand this or else it’s not very useful. Is it


1/ a sequential list of chords for a verse/chorus that only identifies maj/min?

2/ is this related to bar length?

3/ can ii be the same chord as vi ?


Why not just identify the chords clearly as in D11, Em9, F#7, G…?

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The roman numeral chord system is a formula that can be applied to any key.  Where as using literal chord names are used for a specific key.  


ii7-V7 in the key of C is Dm7-G7 -  G is the fifth note in the key of C hence the G chord it is the V chord in the key of C


ii7-V7 in the key of Eb is Fm7-Bb7.  


The keys are different but the relative relationships between the chords are the same. 


If you are familiar with the formula this makes transposition easier and allows for a concept to be realized in all keys.



While the songs listed are in different keys the progression remains the same.


Same with 



As an anecdote the "Axis of Awesome"  Transposed songs from the original keys to the same key so that the performance would be more homogeneous.

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ok I get it.

It looks like a clumsy sort of system though.

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