Glyn Barnes
I am trying to get my head around chords for use with a melodic minor scale, or more precisely what I have seen referred to as "classic" melodic minor where the scale has different notes ascending and descending.
This is not something that can be answered in a paragraph. Walter Piston in his book Harmony (which a lot of people consider to be the bible of that topic) takes a full five pages to discuss this. Here are some highlights (if I may be so bold as to pretend I have expertise in this area).
The main contention is between a minor seventh vs major seventh. The minor sixth vs major sixth also has conflicts, of course. One important factor is whether a note is in the melody. If it is, that normally trumps everything else.
But the rest is largely context. The seventh will almost always be major if the following chord is tonic (at least until the latter part of the nineteenth century when the period of common harmony practice was coming to a close). When resolving to tonic, the seventh really demands to be a leading tone - in other words a major seventh. However, if the chord is III, the seventh will be minor. If the chord is the triad that starts on the seventh, then the seventh will be minor if the chord is V of III (that is, if the following chord is III which V of III nicely resolves to). On the other hand, if the that chord resolves to tonic, then the leading tone factor again makes a major seventh imperative, making the chord a diminished triad.
Maybe Mr. Piston was just trying to say what we already know: if it sounds good it is good.
