·      As well as the four important chord types we already encountered (Δ7, -7, 7, Ø) there are a few others that do not come from harmonising the major scale.  To understand the origin of these chords, we need to look at a couple more scale types used in jazz.

·      You recall the point that was made about the tricky status of the fourth in relation to major and dominant chords?  It was mentioned in passing then that one way of dealing with the problem is to sharpen this note.  This gives us a new scale (the lydian scale), different from the major scale.

 ·      All the lydian scales are shown here.  It would be instructive to harmonise the F lydian scale and compare the chords you get with those of the harmonised F major scale.  See if you can work out the names of the three new chords.

 ·      The harmonised lydian scale does not throw up any chord type that we haven’t encountered before.  But look at the second scale - the lydian augmented.  Now we find something new.

 ·      F lydian augmented is the F lydian scale with an augmented fifth in it.  That is, C is raised to C#.  This is a very nice scale and important in jazz.  Using this scale in your improvisations, particularly when you’re exploring minor and dominant seventh chords, will make you sound more like a legitimate jazz musician!

 ·      Harmonise the lydian augmented scale.  Now you’ll come upon chord forms we haven’t discussed before.  The triad on I has a new structure - a major third followed by another major third (in F, that would be F:A:C#).  The presence of the augmented fifth (F to C#) gives this chord its name.  Its symbol is Faug or, usually these days, F+.

 ·      The full symbol of the four-note structure on degree I of the F lydian augmented scale (F:A:C#:E) would probably be F+Δ7, F augmented major 7, though in practice you don’t often see it.  You do sometimes come across the form +7, augmented dominant seventh.  F+7 would be F:A:C#:Eb.

 ·      Another new structure will turn up when degree VI of the lydian augmented scale is harmonised.  In the F scale, this means D:A:F:C#.  The basic triad, D:A:F, is D minor, so the chord is basically D-something.  D to C# is a major 7 interval.  This makes the chord D-Δ7 (D minor major 7) - a very nice chord, and with the -7 a handy variant on the straight minor.

 ·      Once again, augmented and minor-major seventh chords have improvisation scales derived from their parent scale, which is the lydian augmented.  But notice also that the harmonised lydian augmented scale also includes familiar chords from the harmonised major scale.

 ·      For example, G7, A7, BØ and E-7 all occur in the harmonised F lydian augmented scale.  So if you came across one of these chords when playing in quite a remote key, you could use the notes of the F lydian augmented scale in your improvisation.

 ·      Think about it - the II-V-I pattern in the key of D is | E-7 | A7 | DΔ7 |.  You could improvise on this using just selected notes from the D major scale.  But now we know that the harmonised F lydian augmented scale includes both E-7 and A7.  So you could introduce some really quite sly and oblique melodic ideas in the first two bars by exploiting this relationship before slotting back into the “true” key (D major) for the last bar.

 ·      These ambiguities of parent improvising scale give modern jazz some of its distinctive flavour.