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.
Some 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:
|Original triad||Add 4th note||Comments|
|I and IV major||Major 7||Unless root is in melody|
|Major 6||Can use if root in melody.|
|Minor 7||Only for blues|
|Passing diminished||Diminished 7 (= maj 6)|
|Diminished (chord VII)||Minor 7||Minor 7 b5 (half diminished)|
|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|
|Major chord bVI||Major 7|
|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|
bVIis 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.