There are 3590, totalling over 220 hours. That's over nine solid days (the full twenty four hours) of music.
That's a hell of a lot of music, and it doesn't even include most of my CDs (I have perhaps five CDs that I own copied to my computer) or music that I don't have a music file for, but a video file (that is, I have the music video downloaded but not the song itself).
I've even listened to, uh, pretty much every song there at least once, though there's some new stuff I haven't had a chance to listen to yet.