I like to listen to music at work. Sometimes I just stream from YouTube, Soundcloud, Spotify or some other online source but if you're a person of a certain age, like me, you probably have quite an mp3 collection. All those CDs that have been ripped not to mention some converted vinyl. I used to use the Music Player Daemon or MPD back in the day. It would run in the background and you could connect to it using lots of clients.