Thanks a lot for your effort, trondis. Very kind of you to help a bloody beginner like me ;) My RPi is about to arrive Tuesday, so I will dive into your suggestions then. I am really curious if I'll get everything working, will post here if I succeeded or not. Have a nice rest-weekend, best regards ...

Recently I have started to use another program for music: Squeezeplug. The first time I tried it it wasn't gapless, and had other problems as well. But the most recent version, if you use the Squeezelite player, is gapless. I am controlling it from my Android phone. I didn't realise how good it was...