If you are using the tablet as a "fat" client, which it sounds like you are, then the client player is responsible for audio playback. If your player is configured properly within the fat client xlobby, you should be able to hear the music playback on the individual player as it is streamed across the LAN from the server. Personally, I have never used the internal player to the new xlobby versions, so I don't know how well that is integrated. I use winamp, which on the fat client has to be configured, just like configuring a standalone xlobby version.
Sorry I missed your questions from before.
Can I install on the tablet a thin client? Give it there another version of xlobby?
A thin client does not use any install of xlobby. It uses the client software found on the server xlobby. You would copy the xlobby2sd.exe program and server.txt over to your tablet. Then you have to set up the server.txt file to the IP address of your server. All database run off the server. All music is run off the server. The only thing a thin client does is control the server thats it. This means that your server would require the soundcards for each zone and a player dedicated to each soundcard output.
A fat client is the ability to run a full version of xlobby. All databases are copied from the server on startup (of the fat client). All music/video/pictures...whatever stays on the server and is streamed over to the client. What this means is that each client will require their own soundcard and player dedicated to drive that clients output...and xlobby on that client to control the player. To that individual client, it would be like your just operating winamp. To the server, or other clients, this fat client would be seen as a zone, and can be controlled from any other client, or from the server itself.
I hope this helps.