"No music"

[tatami]

I've been using MinimServer on my iMac to stream music in my iTunes library to a Yamaha WXC50. Last night, instead of MinimServer showing up under the Server button of Yamaha's MusicCast app, it just says "No music". The only thing that's changed is that I've been splitting many albums into smaller "albums" – eg two symphonies on a single "disk" have now become two symphonies, each on a "disk" of its own.

FYI, this problem happens with both my iPhone and my iPad, and I've tried restarting MinimServer. No joy. And my iMac is connected to the Yamaha via ethernet.