The second constraint on the song writing process was modal. I decided that there should be six songs in each of the first six modes (Ionian, Dorian, Phrygian, Lydian, Mixolydian, and Aeolian).
The third constraint was that one song of the six in each mode should start from each of the first six notes in the C major scale, C-A.
I decided that the themes should also be distributed across the structure in a regular way, and arrived at the below chart (the entries in each cell refer to the themes I had decided on, love, drinking, soldiers and sailors, nature, death, and work).
I used this chart to help me find appropriate sets of words (if I had the beginnings of a tune in the Lydian mode staring on D for instance, I knew I had to find a set of words on the theme of death). The chart also helped me to write tunes for lyrics I had already selected - if I had a set of words I liked on the theme of work, for example, I could try to write a melody in the Ionian (which is the major scale) starting from A, or in the Dorian starting from G, and so on.
What is a mode?
One of the joys of this project was learning about modes and how they work. Some explanations can make the modal system sound very complicated, a danger I will not entirely avoid. But although it can sound complicated when put in words, the basic principle is quite simple.
At its most basic, the different modes consist in different distributions of whole and half-tone steps across the steps in an octave scale. But these distribtions are not random. To understand exactly how they are patterned, we need to run the risk of a little bit of complication.
The major scale (C to C on the piano using only the white notes, for example) consists of a certain distribution of whole and half tones across the steps that make up the scale. The first step is a whole tone (from C to D), the second step is a whole tone (from D to E), the third step is a half-tone (from E to F - as you will see if you look at a piano keyboard, there is not black note between these two notes), the fourth step is a whole tone (from F to G), the fifth step is a whole tone (from G to A), the sixth step is a whole tone (from A to B), and the seventh and final step is a half-tone (from B to C). We could write this out as below (with T for whole Tone and H for Half-tone)
This major scale is the Ionian mode (number 1 in the table above). This list of whole and half-tone steps gives you the basic recipe for running between any note and its octave whilst remaining in mode. Thus, if I was to run from D to D, I would make two whole tone steps (from D to E and then from E to F sharp), a half-tone step (from F sharp to G), three whole tone steps (G to A, A to B, B to C sharp), and then a final half-tone step (from C sharp to D). And so on for all other notes (yielding in this case the familiar major scales).
To get to the next mode, the Dorian, one takes the first whole tone step from the beginning of the Ionian sequence and puts it on the end instead. Thus
If one follows this recipe for the notes from C to C, one gets a T (C to D), a H (C to E flat), a T (E flat to F), a T (F to G), another T (G to A), a H (A to B flat) and a T (B flat to C). Following this recipe from any starting note will yield the dorian mode running from that note to its octave (follow it from D and you will stay on all the white notes).
To generate the other modes (Phrygian, Lydian, Mixolydian, Aeolian, and (unused by me) Locrian), one continues to follow the procedure of taking the step at the beginning of the previous sequence and putting it on the end. Thus the complete list of recipes for the modes looks as follows
You will find that if you follow the recipes for each successive mode from the successive white notes of the C major scale (so Dorian from D, Phrygian from E, etc) you will always stay on the white notes. But the tone/half-tone recipes given above allow you to work out the notes in any mode starting from any note.
Having estabished which notes are in the mode, one can then determine which chords are in the mode. Take the example of the Phrygian mode starting from E. Then E minor rather than major is in mode (since the notes E, G, B are in the scale rather than E, G sharp, and B). So is F major (F, A, and C are all in the scale). And so on.