People want a little music to give add to the audio aesthetics, but not take focus away from the conversations & networking etc.
What you want is called
Downtempo or Chill
Some examples
http://www.di.fm/mp3/chillout.pls
http://somafm.com/play/lush
http://somafm.com/play/groovesalad
While this may not be the type of music that people want when they want the music to be the center of attention, it's the kind of music to enhance the experience without being a distraction.