Thanks for the references, Jack. The second one looks like it will be pretty interesting to go through.

But on these threads, I think "Don't try to make it more complicated than it already is!" is a good principle to stick to.

Modes are alternative arrangements of steps and half-steps within scales. It's not a case of "were," it's a matter of "are." Many modern composers are making use of modes, and they're not necessarily trying to sound medieval. Far from it. Nor am I advocating trying to make, say, guitar accompaniments for a folk song or ballad that's in one of the modes sound "medieval," although if one knows what one is doing, this can often be done with good effect.

But the question was, "Musical Modes … Anyone Understand?" The answer is "Yes." And they're not that difficult to understand if you look at them as simply alternative arrangements of steps and half-steps in the scale. And if you want to accompany a song that happens to be in a particular mode, without "clanking," you need to adjust your chords to include only notes contained in the scale.

This is not as difficult as it may sound. Case in point:   in Joan Baez's recording of "John Riley," the melody is Dorian mode. This is the same as the natural minor (A B C D E F G A) with the exception that instead of a half-step between E and F, it is a whole step (E to F#). The primary chords one would use to accompany a song in natural minor a Am, Dm, and Em. The Dm chord contains D, F natural, and A. But the Dorian mode does not contain an F natural, it contains an F# instead. So—instead of a Dm, you play a D major, which is made up of D, F#, and A.

Simple as that!

This does not mean that your guitar accompaniment is going to sound like you're playing it on a medieval citole.   If you want it to, you're going to have to work a little harder than merely selecting chords to fit the mode.

Don Firth