There was a great shift in classical music between the Romantic and Modern periods. Modern communications is a large part of it. Thanks to the phonograph and the radio (which have developed into the iPod and the Internet), people can access music without performing it themselves. Music went from being an activity to being a passive pleasure. There were hundreds and hundreds of piano manufacturers at the turn of the last century (1900). Now there are 50 or so. In the 19th century amateur involvement with classical music was extremely high. The middle class all owned pianos, and they played music of the great composers. As soon as Schumann, for example, published a new piece, it would be purchased and played by amateurs throughout Germany and Austria (and much of the rest of Europe). Symphonies were always released in 4-hand or 2 piano transcriptions, and that's how people became familiar with them. Amateur choirs were common. Music, specifically classical music, was THE pasttime of the educated middle class.
Once the phonograph became available, it was no longer necessary to make music oneself, and so it essentially stopped. The mass dissemination of music that came about through radio led almost immediately to a great democratization of music, so that all sorts of music became available, and much of it was not from the middle class. Music had ceased to be what people did in their homes and became what people listened to in their homes. Naturally classical music, which has a level of complexity that requires some study, became less popular.
Also, composers starting with Schoenberg took classical music to a place that most people just couldn't follow. In freeing music from harmonics, it became difficult even to listen to for most people. Even intelligent, caring, educated people could not abide atonal music. Music had gone from being a middle-class activity and product to being an activity and product of a few elite. Composers no longer cared what the public thought of their work -- they weren't composing for the public at large anyway.
How composition got to this point in the early 20th century is probably very complicated. At least part of it was World War I, which fractured the Western world's sense of connectedness and made every man a cynic overnight it seemed. Part of it was the natural development through the Liszt and Wagner lines -- both in terms of the music itself (increasingly chromatic and verging on atonal) and in terms of the attitude of the composers (it's all about me, me, me).
Huge books have been written about all this. Bottom line for me -- in a very real sense classical music is dead. We are it's museum keepers. Sure there are millions of us, but we are as nothing compared to the billions to whom classical music means nothing and to whom mass market music IS music.
Dumbing down is the ultimate result of all democracy, and democracy is the result of the free and easy flow of information. If everyone is an arbiter of taste, and if everyone gets a vote, then the most popular forms of entertainment will always win out. Capitalism merely rewards those who get the most votes. Classical music can only be preserved in strong socialist countries where it is subsidized by the state.
I read somewhere recently that some organization representing the symphony orchestras of the Western world (North America and Europe) forsees a severe shortage of performers on certain instruments (viola, French horn, oboe, bassoon, etc) to the point that they believe there just won't be enough players to go around in 10-20 years.
If classical music isn't dead, it's certainly moribund. We are but acolytes at the crypt!
Topic: Is classical music dying?