Beets is a media library management system designed for obsessive-compulsive music geeks. It catalogs your collection, automatically improving its metadata as it goes using the MusicBrainz database. It also downloads cover art for albums it imports. Then it provides a bouquet of tools for manipulating and accessing your music. Beets also includes a music player that speaks the MPD protocol, so you can play music in your beets library using any MPD client.
Plgen (Playlist Generator) is a tool that sorts files for MP3 players in a user defined order. Cheap MP3 players often come with no playlist capabilities. In addition these players often make use of the FAT16/32 file system, leading to confusion when the playing order is not alphabetical on the device even though it is shown as alphabetical in the file explorer.
Peyote is an audio player with a friendly MC-like interface. It is designed specifically to work easily with cue sheets. It plays wv (wavepack), WAV, FLAC, APE, Ogg, WMA, and MP3 formats. It supports ID3v2, APEv2, FLAC, and Vorbis tags; multiple playlists; and tabs. It can copy, move, remove, and rename files.
wave-player is a remotely-controllable music player (frontend) connecting via HTTP calls to a music database (backend). It allows music to be controlled and streamed via HTTP so you can hear your music at work or anywhere else. The frontend is based on QT4 and the backend uses via Perl/MySQL. The API is open and REST-based.