Great idea but I just want to mention that Steve Roud's on-line Folk Song Index has a similar feature. IE, each song entry has a link to Google maps, so you can see where the song was collected.

I've been using the Roud index for years and didn't realise that feature was there - thanks for the heads up.

Naturally, I now want the inverse index: given an area, what songs were collected near there? It should be relatively easy given they have the normal index, so I've emailed them with this as a possible future enhancement - unless someone knows it is there already!