Silbo Gomero language

Silbo Gomero (Spanish: silbo gomero [ˈsilβo ɣoˈmeɾo], 'Gomeran whistle'), also known as el silbo ('the whistle'), is a whistled register of Spanish used by inhabitants of La Gomera in the Canary Islands to communicate across the deep ravines and narrow valleys that radiate through the island. It enables messages to be exchanged over a distance of up to 5 kilometres. Due to this loud nature, Silbo Gomero is generally used in circumstances of public communication. Messages conveyed could range from event invitations to public information advisories. A speaker of Silbo Gomero is sometimes referred to in Spanish as a silbador ('whistler'). Silbo Gomero is a transposition of Spanish from speech to whistling. This oral phoneme-whistled phoneme substitution emulates Spanish phonology through a reduced set of whistled phonemes. It was declared as a Masterpiece of the Oral and Intangible Heritage of Humanity by UNESCO in 2009.

Little is known of the original Guanche language or the languages of the Canaries, but it is assumed that their phonological system must have been simple enough to allow an efficient whistled language. Used by the island's original inhabitants, the Guanches, the whistled language existed before the arrival of Spanish settlers and was also spoken on el Hierro, Tenerife, and Gran Canaria. Silbo was adapted to Spanish during the Spanish settlement in the 16th century and was widely spoken throughout the period into the following 17th century. In 1976 Silbo barely remained on el Hierro, where it had flourished at the end of the 19th century.

...
Wikipedia