Folderity

Folderity is a fast and lightweight music player that allows you to create custom playlists that are bound to folders on your PC. Whenever a song is added or removed from the folder, this change is reflected in the playlist. This is very convenient for anyone with a large collection of music files (MP3s, WAVs, etc.) since it allows the user to automatically organize their music into playlists without being forced to manually add songs to the playlists one at a time. Instead, the songs are added and removed from the playlist, as the folder's contents are updated.