I've got several Pi3s with HifiBerry boards around my house. All running piCorePlayer software. I use one of the them as a Squeezebox Server (LMS), and through that listen to radio streams on all at once, just what I want.
But when I want to choose my own music, I like to use Spotify. I can do that through the app under Squeezebox (and play on all Pis at once), but the interface is poor compared to the "official" Spotify running on my iPad.
I can use the Shairport Sync receiver on any one of the Pis to link to my iPad, but I can't link to all at once. What should I be using to be able to link audio output from anything on my iPad to all of the Pis running Shairport Sync, at once?