Tanks a lot jotak for your explanations!
So, I changed the lines as stated, but I still had artist names repeated. In my case the reason was, that the affected artists were assigned to different genres. I have many artists where this is the case. So, that´s not the showstopper, I can live with that. But still there are not showing up 20% of my covers.
I´m using MPRemote. In every album where the cover is missing, the titles 08 and 09 are missing there numbers and they are moved in front of all others. So, you will see 2 titles without numbering and then going on 01, 02 til 07, 10, etc. . That´s strange and it happens allways with the same albums. I don´t know, why this happens…
Volumio as a player ist great, but I need a client, which has a wall of covers or at minimum a cover beside the album name.
In MPDroid I only get covers when I choose an artist and the local covers are not loading automatically. Besides in this program I´m loosing from one second to the other 90% of my library (ca. 500 albums).
sound@home has no covers on a selection side, you have to navigate through folders.
Mupeace: the covers are not loading, only large album covers could be displayed (that makes 2 side by side in 250 rows).
Droid MPD Client: Covers only when music ist is choosen or playing.
So, that are all clients which I know for an android tablet. The woman acceptance factor for all of this programs is still negativ.
In the meantime I have to stay with OpenElec and Yatse as client. With that client my wife can handle the thing. But with OpenElec you will have resampling to 48 khz… so bit perfect playing is gone.
So the search goes onward…
Anyway, thanks a lot for the help and if anyone has found a good working client for Volumio with cover displayed for selection, please PN me!!!