Yet another Fedora saga. Interpreting the fedora forum messages, there's some hassle about the audio interface/drivers not getting sufficient priority on interrupts. The symptoms are that audio (I was listening to some mp3 files on rythmbox) 'stutters' and clearly isn't getting enough data to keep up.

The solution was, as root

$ yum remove pulseaudio

which did remove a few other packages using pulseaudio, but never mind. Then went into the sound setup and selected Alsa as the sound source/sink. Now sat here listening to glitch free audio (again). I hadn't realised how much I used it!)

This thread shows the solution (eventually). This is what I was trying to play. I'd enquired of Amazon (UK) about it, but they're clearly too busy.... or something. Not a dickie bird from them, well, they'd had my money.