This is the very core of EMMS. It provides ways to play a track using `emms-start', to go through the playlist using the commands `emms-next' and `emms-previous', to stop the playback using `emms-stop', and to see what's currently playing using `emms-show'. But in itself, this core is useless, because it doesn't know how to play any tracks --- you need players for this. In fact, it doesn't even know how to find any tracks to consider playing --- for this, you need sources. A sample configuration is offered in emms-setup.el, and the Friendly Manual in the doc/ directory is both detailed, and kept up to date.