Yes, that is possible. Use the P-Mute function on your Beo4, then the screen switches off and normally Speaker-Mode 2 is activated, if that is the default audio speaker-mode. This has to be done every time you want to listen to digital radio. On a Beo5, you could programm a button to switch on radio and mute the picture at once. Ask your dealer about that if you have a Beo5.
Music washes away from the soul the dust of everyday life. - Berthold Auerbach