Half way through the hex
This slightly absurd structure that I have imposed upon myself is actually turning out to be really helpful though. I now have somewhere to start when faced with a set of words, say a lyric in the theme of 'drinking'. I can see what is left as far as that theme goes (at the moment in this case G4 and F5) and know that I need to try and write a melody either in the Lydian mode that starts from F or in the Mixolydian that starts in G. And that constraint is useful. It is also useful, mind, to be able to go back to the archive and search out different lyrics on the same theme when none of the ones I have left seem to work.
The really nice thing is how working in these different modes gets you away from the tyranny of the three chord trick. I could have sat down and written tunes to these lyrics without all this palaver and a lot of them would have been three chord tricks and a lot of them would have sounded fairly similar and it would have become rather boring. But the chord sequences that these modes impose are seriously weird. Or at least take a bit of getting used to. For example, take the Phrygian starting from D. D minor is in mode, but then so is C minor. I mean, I have lost count of the songs I have written that go from D minor to C major, but those two minors together like that is quite a trip. And then, of course, E flat major is in mode too. I haven't quite worked out a way of bringing in that second step chord in any of the Phrygian songs that I have written without it sounding just crap yet (but then there's still one more of them to go - starting from C and about sailors/soldiers).
I know enough about harmony to know the three chord trick, and then the minors that you can use in key. I also grew up with those old dixieland and jazz tunes from the thirties, and so I also know the 'extra' chords they often use (your D7s and A7s in C for example). But the thing is, even though these extra chords are not in key, they are modulations away from the major key, and that major tonality remains dominant. This modal stuff is something else.
I am recognising hopw a few of those 'tricks' we often use as songwriters are modally based. For example, you've got a tune in G and you've gone to C and D, you've put in an Em, even an Am. So then you stick in an F. Not in key. But it is in mode (in the Mxolydian mode). But the Mixolydian mode doesn't have a D major - there is no F sharp. It has D minor instead. So most people don't stay in mode and the major scale remains dominant.
Mind you, my goal is (rather with the way the sonnets are hidden in The Ozzard of Wiz) that all this structure stuff won't really be apparent to the listener - that no-one is going to find that any of the songs strain against their mode; rather that you just hear a nice melody. Well, we'll see how that goes when it's all done.