Jazz Arranging: Reharmonisation

REHARMONISATION

In some cases reharmonisation is necessary before arranging for jazz orchestra or combos. Most sheet music for popular music standards of the 30s, 40s and 50s will include chord symbols, but in some cases these will be wrong, too simple or too complex.

Some publishers of sheet music invert a min7b5 so that it becomes a min6:

Ex 1

This is done to simplify the chord symbol for guitarists. The inversion makes no difference to the overall harmony if played alongside a bass instrument, but as a given chord symbol it implies the wrong bass note. A genuine m6 chord is usually either a tonic minor, or a IVm6 as part of a IV- IVm - I (plagal cadence). If it appears to be part of a IVm6 - V7 - I progression the chances are it is an inversion of II should be changed to IIm7b5 - V7 - I.

In mainstream jazz four note chords (7ths) are usual. Most sheet music will include four note chords (7ths and 6ths), but with other material (eg folk tunes) you will need to adapt triads according to the table below:

Major keys

Triad	4th note	Comments
I and IV major	Major 7	Unless root is in melody
	Major 6	Might sound cheesy. Use if root in melody
	Minor 7	Only for blues
V	Minor 7
Minor	Minor 7
Passing diminished	Diminished 7 (= maj 6)
Diminished (chord VII)	Minor 7	Minor 7 b5 (half diminished)

Minor keys

Triad	4th note	Comments
Minor chord I	Major 6 or 7	Can be dissonant or cheesy
	Minor 7	Modal feel, may not always sound final
	None	Triad sometimes sounds best
Diminished chord II	Minor 7	Minor 7 b5 (half diminished)
Major chord IV	Major 6
	Minor 7	Bluesy (can sound like dominant of bVII)
Minor chord IV	Major 6 or minor 7
V	Minor 7
Major chord bVI	Major 7
	Minor 7	Bluesy
Minor chord VI	Minor 7
Major chord bVII	Major 7	Dorian
	Minor 7	Aeolian (beware, sounds like V7 of III major)
Minor chord VII	Diminished 7

• bVI is used to denote chord built on minor 6 degree of scale, eg Ab in key of Cm or F in key of Am.
• A major or minor 6 chord does not have a 7^th, otherwise the chord would be a 13^th.