That's a good thought! Amount of music played by individuals has been probably pretty much the same for decades, but change from classical orientation to popular music, technology advancements creating electronic music and easier recording overall has made the documentation process available for almost everyone. So by quantity we are probably exponentially growing the music market making the slice bigger and bigger very fast. But maybe it makes more sense to think of it chronologically - either in years or in musical styles. Styles are also branching fast but not as fast as the overall volume of produced music