I re-edited that tutorial quite extensively a few months ago, you might like the current version better.

There are quite a few "simple explanations" around on the interweb, and I have problems with all of them. Mostly, they present something that isn't any obvious use for the traditional musician. OK, you can classify the tunes you perform according to a scheme somebody thought up for an entirely different kind of music a few hundred years ago. So what? Why should anybody care?

With the extra detail the gapped-scale system gives you, you can do far more - once you listen to the examples, you can hear how some melodic patterns are typical of certain modes, and you hear how the modes help you *express* something. (Look at the examples of gap-filling development). Knowing where the gaps are and what the common patterns are, you can play tunes better, or improvise on them in ways that will sound more idiomatic. If your instrument has diatonic limitations, you can use the modal structure to play stuff the standard key signature would tell you you couldn't. You can memorize tunes easier.

However, going into intonation is *too much* detail. There are many different intonation schemes you can use for any one mode - Dorian mode is recognizably itself whether you render it in equal temperament, Pythagorean, the classical Turkish system, third-comma meantone or whatever.