mpd

Daemon to remotely play music, stream music, handle and organize playlists. Many clients available.

Similar alternatives

Modern Music Server and Streamer, compatible with Subsonic/Airsonic.

Personal music streaming server that works.

Music library manager and MusicBrainz tagger (command-line and Web interface).

Audiobook and podcast server. It streams all audio formats, keeps and syncs progress across devices. Comes with open-source apps for Android and iOS.

Extensible music server. Offers a superset of the mpd API, as well as integration with 3rd party services like Spotify, SoundCloud etc.

Synchronous multiroom audio server.