I came across this in another forum. I thought the person concerned had something interesting to say so I kept it. It refers to instrumental music rather than song, but much could be applied to song:

Traditional music, in my opinion, harks back to a time when communities were a horse ride away from each other and styles were localised. Tunes would be played at celebrations and would be known tunes within a particular community or group of communities. At weddings and other celebrations, dances would be a form of community bonding. Knowing the steps would be a form of cohesion, of belonging. New dances and styles would be slowly absorbed from the periphery, variations from the next village etc. Occasionally a newcomer would bring something new – a new instrument, a new dance a, new tempo, a new variation. This would be absorbed into the culture and molded into the repertoire. The industrial revolution started to distort traditional music, through mass migration, and the opening up of even the most isolated communities to the world. At the same time collectors with wonderful foresight started to gather tunes from areas, preserving in aspic many of the old traditional tunes, before they were lost. Mass communications, firstly radio, then TV, allowed music traditions to be both preserved, and diluted and distorted and marketed. New tunes in the tradition, so to speak, were composed in their thousands.
Lastly, the Internet has allowed musicians to communicate directly with each other, and express their own views on the traditional music, they can hear tunes from around the world. On the one hand all these modern innovations (from transport, through mass communications to the internet) have diluted traditional music and spread it to the four winds to be played by any musician with a whim to play it. Here in Scotland I can happily collect Appalachian music, Northumbrian music or Japanese music and add them to my repertoire of local tunes. Some I meet will only play local tunes, others have their specialities, cajun, bluegrass, shanties etc etc etc.

The important thing to me is that these tools have also allowed people who care about the traditional music of a locality to study and preserve it too. There will always be people who believe that the music should be preserved at all costs while others are open to any and all influences. One day, with the passing of oil, and mankind being thrown back onto the resources of the local community, the time may come again when a style of music and dance will identify us with a particular locality. Meantime we live in a time of unbounded richness of music, and I for one will play anything if it is a good tune and stirs some emotion in me and those who will listen to me.