Church modes

[BuyBuy]

So about the church modes used in Middle Ages.

I understand the concept that there is a final and an arrangement of whole and half steps that define each mode. I also understand that those tones were not fixed like ours, but rather depending on the pitch of the singer.

But now, who came out with this idea of composing music through modes ? I mean, how was it that it was decided that all modes have only seven notes in it, and not eight, or five for example (like in other cultures' music) ? Anyone with insight on early music history ?

[Nightscape]

Well, as I understand it, almost every single type of scale from any culture is just a division of the octave.  In other words, the scale repeats itself after each octave.  So it could just be coincidence that the Western scales ended up being seven notes per octave - or it could be that the seven note scales are the most balanced division.  The pentatonic scales (5 notes) are more consonnant to the ear, but they have little harmonic use, as the result is a very static new-agey sound.  Since Western music is the only music where harmony developed to be just as important if not more than melody, understandably they would seek out a scale that is pleasing to the ear, yet also has harmonic interest.  Again, scales with more than 7 notes start to sound unpleasant, and even the more pleasing symmetrical ones (like the octatonic, whole-step half-step scale) again have little harmonic use.  But with a seven note scale, you are able to create chords, whether triads or seventh chords that are all either a major or minor third apart.  Try doing that with something like a whole tone scale.  In that case, the result is always an augmented triad, never changing.  So you can see why a scale like the whole tone (6 notes) is not so great for harmony.  But in the modal scales, you can end up with an infinity of sounds.  There are 3 different types of triads (major, minor, diminished) available, as well as 3 types of seventh chords, 3 ninth chords, etc.  And of course those are only diatonic chords.  The great thing about the modes is that you can "borrow" notes from other modes (accidentals) to create even more interesting sounds.