I’ve used Icecast2 + mpd for ages, but in the last couple of years I’ve been using Logitech Media Server (LMS) to get synchronised music playback. It’s mostly good, though quite memory-hungry and a bit picky about permissions. The control of playback via web interface is functional, but I find it clunky. Given there are CLI and json interfaces (even wrappers!) to LMS, it would be nice to have an interface in the style of mpd. Such a project is beyond me time-wise, alas…