Cryptic Map Clue

Here's a little cryptic map clue. Can you name the song from the map?

The map itself was created using the canvas layer utility library. If you want to use the library yourself Pedro Sousa has written up the steps he went through whilst using the library to create a map of all the localities of mainland Portugal. Here's the write-up and here's the resulting map.

Pedro's map contains about 140,000 points and so is a great example of how the canvas library can be used with the Google Maps API to plot thousands of points on a map. My map contains 4,000 points (there's a big clue to the song)