Disney world was one of the first I recall doing this in the 70's and 80's. Now outdoor speakers and technologies are more commonplace.
I think it can add to ambiance in some cases, but in most, it's tiresome background noise. Take a trip to the country or go camping to enjoy the sounds of nature, stillness of the night, and quiet comfort. Noise pollution can be a stressor and I view many of the musak venues as a contributor.
Adam Carolla also has a great take on this subject.