"Soft music was playing in the background," or "through the open window she could hear the clear yet far away pling pling of a piano somewhere," are such romantic novel cliché sentences. But music in the air does add a lot to the ambience, it's one of those quality of life things.
When we have people over I always have background music playing, sometimes more jazzy or bluesy, sometimes more French chanson, sometimes something else, depending on the mood and even theme of the evening. But it's always so soft that it adds to the overall ambience and is only heard in shreds here and there through the hum of the general conversation. When I don't have to concentrate too hard, I may put music on while I work, although that needs to be very soft classical or piano music, otherwise it distracts me.
Music adds festiveness to the mood and softens the atmosphere. Music, like any art, adds to the quality and complexity of our everyday life experience. Without music, or art in general, life is denuded, stark, plain. To me putting on music also signals "special" since I don't have it on all the time. You can also add the frequency argument to the conversation. Since music is or has a frequency, and higher frequencies denote more positive emotions and moods for us, music in those higher frequencies (...not Heavy Metal or Punk Rock) contributes to our overall feeling of wellbeing. Hence allegros are perceived as cheery and largos as composed and serious. Hence also the reason for piping baroque music into the Port Authority bus terminal in New York City.