Re M.Ted's posting: the major/minor system didn't generalize the modal one, it replaced it, and there are places where it gives wrong answers when applied to modal music. If you are trying to improvise on a Dorian or Mixolydian tune, what you play will sound wrong (or at least, obviously different) if you switch to the minor or major pitch set on the same tonal centre.

The music of the Middle East and India is somewhat of a red herring as typically, while they have many more scale patterns, they don't have as many modes as we do. It is fairly common in Turkish music for a scale pattern to have only one mode associated with it, and two (based on the tonal centre and a fourth up) is the usual situation.

Every musical genre has its own special kind of complication that it takes to its bosom and goes overboard with. For Indian music it's microtonal scale patterns, for common-practice Western art music it's harmony, for didgeridoo music it's timbre, and for British Isles folk music it's modes built on gapped scales.