There's a lot of cool GNU/Linux music-playing programs out there. Some of them keep track of your preferences so that you can hear your favorite songs more often in otherwise random mixes, or even strive to balance preferences between multiple listening users.
But I think somebody should start tracking volume changes. This is useful information. If I crank up the volume on a particular tune, it should record that fact. This would count for something in the preference scoring department, and would also enable the building of playlists like, "rock me" or, "me sleep now".
I thought about this when GZA's "Duel of the Iron Mic" came on, and I cranked the headphones up.
Hm, but now Lauryn Hill is on and I'm leaving the volume up, but I'm not going to turn it any higher because my ears will bleed. So maybe what we need to keep track of is the average volume over a session, and then the deviation for each song from that average.
Perhaps then the volume could automatically change with the song.