Documentary exploring the art of whistling and its origins. Whistling has been part of people's lives the world over, and is in fact the most international of all languages. For some it's a hobby, while for others it's a means to making a living. The ancient whistling language Silbo Gomera can be found in La Gomera in the Canary Islands. It was originally used by farmers to communicate from village to village in the island's valleys in the days before telephones. Although once thought to be dying out, the language is now enjoying a revival and is now taught in school.