Ideas are introduced through experimentation, and artists incorporate elements of those ideas into their works. In many ways, music is a tremendous library of ideas that are passed on by methods similar to those of ancient oral traditions. Each generation molds what came before into something new, extending the past out into the future like the limbs of a tree. Branches may intertwine while others fall off completely and are left to decompose. Attempts to exhaustively classify and define this process are, of course, doomed to fail, but we are curious to understand the process, to swim upstream and discover the source.
Stagnation is poisonous to the creative spirit.
This isn't so much a curse as it is a stimulus to keep us moving in new directions. Music has the mysterious capacity to resonate the entire spectrum of emotions. Unfortunately, most of the means yet devised to map out the terrain of human feeling are of limited use in the face of modern technologies and musical forms. Sheet music has been displaced by MIDI data, and few artists emerge from the militaristic territories of classical music instruction with creative instincts intact. To say nothing of the ideological motives of conservatories, much of modern music has grown beyond the scope of traditional music theory.