I noticed that I can sort my active (tons more on backup that I don't listen to much) music collection by year and saw some interesting trends:
Music recorded before 2000 = 11 hours
Music recorded after 2000 = 98 hours
That's a serious skew toward newer music. I have almost nothing from before 1980; a few soundtrack songs from really old horror films. Even the '80s, which represented my musical coming of age, barely total 100 minutes. 10 hours from the '90s, which seems low considering that those were my university years. That leaves nearly ten times that much from this decade, which isn't even done yet.
While I find it vaguely embarrassing to have apparently forsaken most of musical history, I think I know why -- I started living (well, working anyway) online in 1999. That's when my real collecting began, and of course most of the stuff posted and downloaded since then has been newer music. But still...