Unfortunately, no one here has yet to bring up a valid criticism of Philip Glass.
That, of course, is strictly your opinion. I have yet to read a post by you where you demonstrate a clear understanding of this so-called minimalism. Perhaps our criticism of Glass is based on a visceral (and negative) reaction to the repetitive, hypnotic and ultimately soporific effect of his music, but your appreciation is hardly based on a defense that is any more intellectually rigorous.
Let's get your end of the debate started with Kyle Gann's description of some of the characteristics of "minimalism." Gann is an American composer and former critic for The Village Voice. This info comes from the Wikipedia entry on minimalism.
1) static harmony and audible structure
2) alogorithmic, linear, geometric or gradual processes (such as pattern augmentation by 1, 1 +2, 1+2 + 3, etc.
3) a steady beat
4) static instrumentation
5) "metamusic" (unplanned acoustic details that arise as side effects to the performed music)
6) pure tuning
7) influence of non-Western music (African drumming, Indian music)
Using these criteria, we can all agree that Glass uses some or all of these technques here and there in his works. Some of the techniques he uses to such length (and to the exclusion of so many other traditional compositional techniques) that one is compelled to classify him as a minimalist.
No problem there. Nothing wrong with minimalism.
The problem with Glass (and this can only be subjective, no matter how much you demand scientific objectivity from us regarding an art form) is that his basic material is uninspired and uninspiring. Listening to any work of his eventually induces a sense of boredom that comes from:
-- the repetitiveness of his orchestration (i.e. massed strings and woodwinds used exclusively for prolonged periods) with very little change in color.
-- harmonic palette (no more chords than appear in a Britney Spears' song).
-- a steady, (normally) four-square beat that is relentless in its unvarying steadiness.
Just these three items alone spell a gross lack of variety for the ear. It induces boredom. Unrelieved repetition induces boredom. One of the first things any composer learns is variety and just shuffling the same notes and chords about in pattern augmentation (1, 1 + 2, etc.) doesn't do the trick alone.
Wagner uses a very "Glassian" technique in the opening of "Das Rheingold" with the immensely prolonged E-flat pedal and the strings swirling above in arpeggios. But, that's only a starting point for Wagner. He moves on to contrasting material to bring to an end the "river water" trance and to draw the listener back into the drama.
Glass is such a poor dramatist because of his inabilty to offer up any real variety. He's a slave to his technique, which is the antithesis of variety. And any musician who is a slave to technique is probably a slave because real musicality eludes him. In lieu of inspiration, he relies only on technique.
I doubt that this will satisfy your high standards for "valid criticism," so debate these issues in a follow-up post. You seem to have unlocked the secrets of Glass's music that none of us know about. Kindly share.