The agony category is perhaps dominant and includes pieces like this one:
A piece doesn't have to be agonizing all the way through to fit my category. It is enough that the mood is generally unsettled, troubled, with ominous blasts from the brass and percussion. There is a sense of threat always in the background. Many of the symphonies of Shostakovich and Pettersson fit in this category. The other category, trance, might be epitomized by this piece:
The prevailing mood is one of calm and while there may be bursts of activity on the surface, there is an underlying level of stasis. Typically, music like this is slower moving or uses a lot of repetition. Another example would be one of the symphonies of Philip Glass:
I think that this phenomenon, not just restricted to symphonies, by the way, has come about for some historical reasons. The 20th century was an horrific time with the slaughter of tens of millions in war and genocide and totalitarian social experiments. It was perhaps the most inhuman century in human history. Artists recoiled in horror from this and as a consequence wrote agonized music. This stance is impossible to maintain indefinitely so an alternate aesthetic mode was developed, that of trance. The inspiration for this was likely older European musical forms like chant and passacaglia, but there is also an influence from world music. The melodic ideas of Indian music have been an influence on Philip Glass, for example.
The interesting thing about this is the narrowing of aesthetic possibility it implies. We are still so traumatized by the attempted suicide of European civilization in the last century that we are still processing the agony and our only relief seems to be a kind of narcotic, numbing trance...
Or am I oversimplifying? Comments?