Sorry, Mark I realise I am not being clear. Let me try again...

I turn the empeg on, somewhere during to boot phase (probably, but not definitely at the point that it enables the tuner) you hear what sounds like and un-tuned FM radio. I assume that this sound is the tuner, but not tuned to a station.

The empeg then boots into MP3 player mode. You can play MP3s and everything behaves normally, you can hear the MP3s playing.

At the same time however, mixed with the MP3 audio, you can still hear the un-tuned FM radio. If you switch to tuner mode the MP3 stops and you can still here the un-tuned FM.

If you switch back to MP3 the un-tuned FM radio is still audible. The volume of the un-tuned radio sounds pretty much the sound it would if I switched to the radio normally and un-tuned it.

I don't know whether you can tune the radio when it is in this state, I have always pulled and reinserted at that point. I'll have more of a play next time it happens.

This is a factory tuner, if that makes any difference. No extension lead was used when installing.