Jazz Reharmonising

Reharmonising – Changing the Chords

Often you may want to do some reharmonisation 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.

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

 

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

Original triadAdd 4th noteComments
I and IV majorMajor 7Unless root is in melody
Major 6Can use if root in melody.
Minor 7Only for blues
VMinor 7
MinorMinor 7
Passing diminishedDiminished 7 (= maj 6)
Diminished (chord VII)Minor 7Minor 7 b5 (half diminished)

Minor keys

Triad4th noteComments
Minor chord IMajor 6 or 7Can be dissonant or cheesy
Minor 7Modal feel, may not always sound final
NoneTriad sometimes sounds best
Diminished chord IIMinor 7Minor 7 b5 (half diminished)
Major chord IVMajor 6
Minor 7Bluesy (can sound like dominant of bVII)
Minor chord IVMajor 6 or minor 7
VMinor 7
Major chord bVIMajor 7
Minor 7Bluesy
Minor chord VIMinor 7
Major chord bVIIMajor 7Dorian
Minor 7Aeolian (beware, sounds like V7 of III major)
Minor chord VIIDiminished 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 7th, otherwise the chord would be a 13th.
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