On La Gomera, in the Canary Islands, people don't only speak Spanish. They whistle it.
Silbo Gomero is Spanish turned into a whistle. Its roots run older than the Spanish: the Guanches whistled across this island before the ships came, and afterward the whistle was fitted to the new language. UNESCO calls it the only whistled language that is fully developed and still practised by a whole community, more than 22,000 people.
It was made for the ground. Deep ravines, narrow valleys, where a shout dies and a whistle carries. A message can cross up to five kilometres of gorge and arrive understood. It is loud on purpose, built for public things: an invitation, a warning, a piece of news. You whistled, and the valley heard.
Then it nearly went quiet. The telephone arrived, the farms emptied, and the whistle picked up a reputation as a poor man's habit, not something a family wanted for its children. A whole generation grew up able to hear it and unable to answer in it.
The island turned back. In 1997 the parliament of the Canary Islands moved to bring the whistle into the schools; from 1999 it was compulsory in primary and secondary. Old whistlers taught the young ones, and now there is a school for the ones who will teach it next. UNESCO listed it in 2009.
They didn't save it by writing it down. You can't write a whistle. They saved it by teaching it to children, who still send it gorge to gorge.
Sources: Wikipedia, "Silbo Gomero"; UNESCO Intangible Cultural Heritage (inscribed 2009); La Gomera tourism board. Photo: Akalvin, photographed on La Gomera, 1991. CC BY-SA 3.0, via Wikimedia Commons.