Peter, what is is with you? All you ever think about is modes;-)

Modal music tends favor that full step drop, in fact, the turkish Saz has, in addition to the melody and drone strings, a string that is tuned a full step below the melody string so you can bop down a step without moving your hand----(It get's a bit dicey when the you are up the neck on one of the quartertones(well, actually more of a 2/9ths tone, but that is another discussion entirely) and the "drop" note is not in the mode you are in)--

If you want to understand modal music a little better, check out the bagpipes or the Appalachian dulcimer, which are modal instruments--The scale is irregular--which means that some of the half and whole steps in the scale are bigger than others, and for harmony, you have drone notes, which do not change(as diatonic chords do) to accomodate the melody note-Which means that some times your hear a nice thirds and fifth and sixth intervals, and sometimes you hear not quite so sweet a second or seventh or fourth intervals--

You either like the sound, or you don't, and a long time ago, the people that didn't like it got together and dumped the drones, re-tuned the instruments so the intervals were even, and wrote everything so it was harmonized in major or minor chords--

Anyway, back to my point(if I had one)--The way to create interest in modal music is to repeat a melodic phrase starting on a different note of the scale--(this is called changing the tone center)--Though this seems simple enough, it offers a lot of surprising possibilities, First, because the intervals are irregular and nature of the melody changes, and second, because the of the different sorts of tension that each tone center creates against the constant drone--