Itunes, I use the smart playlist and playlist folders a lot to organize sets of songs in playlists, sub-playlists and sub-sub-playlists
mostly it's two sets of folders, MTR aka My Top Rated, stuff I've marked with five stars, and NRY aka Not Rated Yet, new songs that I haven't rated yet.
The whole Itunes music library is 6070 songs, 12.2 days 39.44GB
The root MTR play lsit folder is only has 949 songs, 2 days, 5.97GB
and the root NRY play list folder as of now has 1466 songs, 1.7 days, 15.95GB
The music comes from the folder G:\music (76.6 GB) that is where we keep our family's music, along with copy on Alam's PC for backup/syncing/network playback.
There is a sub folder name Sorted for songs sorted through MusicBrainz to be correctly tag with ID2.4/UTF16 for MP3 files (there are also FLAC, and Apple lossless m4a files too in there), and placed into sub folders by artist and album.
Another folder call shared with sub-folder for each member of the family, for new songs they wish to be added in the music library.
Desorted for songs Sorted by hand with info not from MusicBrainz
and unsorted folder for albums I haven't not find verified information on.
I use Itunes DJ to do shuffle play with history tracking of on my two main play list folders, depending on if I want to to new music, or my favs.