The history of opera and ballet, not to mention chamber music, is a bit different but still responded, in part, to some of the same pressures. Some of the consequences include the marginalization of non-German composers (except in opera and ballet, again, where the Italian, French and Russian schools were just too powerful to be marginalized!), music outside the mainstream and the fact that it made breaking into the "standard repertory" very difficult for new composers. Various ways were found, however, but it is worth noting that the development of artistic 'manifestos' by people like Wagner, Schoenberg and Stravinsky was at least partly because in order to break into the concert hall, they needed a 'story'.
Music always has a social context but while acknowledging the truth of this, I want to raise a small voice for the sheer pleasure of enjoying music without concerning oneself so much with this. When you find yourself questioning the ideological foundation of every quarter note, it is time to give it a rest. There have always been composers that were working in the very cauldron of social ferment (does one ferment in a cauldron, or is that a mixed metaphor?), but alongside them, there are always composers who are less imbricated in the social context, at least in the way they write their music. If you look back at my last post on ten great little-known pieces of music, I think that most of them could stand as examples of music that is less connected with a particular social or political context. The Beethoven and Shostakovich might be exceptions to this. And of course all music, even the Plainte by Froberger, still arises out of and is understood to be within a social milieu.
But still, when I sit down to write a piece of music, all this is the furthest thing from my mind. I'm trying to do something interesting, fresh and expressive and these kinds of goals are ones I share with countless composers over hundreds of years.
So, to finally get to the theme of the title of this post, I think that the category of great music (I wish I could find a more neutral term for that as calling some music "great" and other music not has often been an ideological ploy) and the category of standard repertory are somewhat different. There is a lot of overlap, of course. Bach and Beethoven, despite whatever ideological juice you can wring from their music, are also great composers in a more neutral way. I guess, by saying this, I am making the claim that there can be neutrally 'great' music or that some music at least, can be considered from such a stance. Maybe that isn't possible... But the fact that we 21st century, non-Lutheran, non-Christian, non-18th century listeners can get such a kick out of a Bach cantata tells me that there is music that transcends whatever ideology it might have participated in at the time of its composition.
Praise Bach in all the lands! Two last things to note: knowing something about what social and ideological influences may be present can add a lot to one's understanding of the music. Only rarely might it cause you to lose interest in some music. Also, it need not matter at all. The fact that Bach praised God in his music doesn't detract at all from its spectacular quality, now does it? Secondly, the standard repertoire is never static. It is in constant flux as some composers are down-graded over time and new composers fight their way in. And the very nature of the repertoire and what purpose it serves changes over time. Right now we are at something of a crisis in 'classical' music and what it will look like fifty years from now, no-one can say. I'm pretty sure that Bach will still be around, though.