Beginning 7 bars of 1st movement. We can observe in the purity a contradiction between music and "symmetry".
Example 1 Beginning 7 bars
Twelve tone is symmetrically arranged. It is an obviously typical mirror form. Although it seemingly seems to be a perfect symmetry, if observing attentively, then you will find that rhythm is not symmetry and that the long value ( eighth note ) becomes short ( sixteenth note ) and vice versa. If arranging the rhythm, too, symmetrically, the mirror form of the look will have collapsed. Is it really symmetry or not? Let's attempt to make this mysteriousness clear. Learn the following example. It will show you an order of the way of thinking.
Example 2 complete symmetry
Arrangement of the notes which doesn't put rhythm either note value in consideration is shown. It is a complete symmetry at this level. (Pay attention to the numbers.) On the arrangement, a process to specify note value and a figure will come. Unless destroying this arrangement, the symmetry on the rhythm is never generated, and the reverse of the value is inevitable. It becomes so automatically and it's not musical matter, maybe. As the example, in following case, only sixteenth notes, the symmetry on the rhythm will not become a problem. And this lacks the depth as music.
Example 3 only sixteenth notes
Symmetry on the sight and symmetry on the rhythm are incompatible.
Because they have no relation each other essentially.
Here in the webern's composition, the visual symmetry is had priority over.
Originally, symmetry is a concept on the sight, and the fact that rhythm is symmetrical is contradiction and impossible.
Because it is time.
As a composition factor on music, symmetry concept is useful, so "composition" is often visual matter. But we've found that "symmetry" isn't based in the fact of "music" in the purity here by the webern's case.
In this case, a perfect symmetry on the sight is formed on an asymmetry on the rhythm. It's very interesting, isn't it? Perfect symmetry is always avoided.