You might be wondering “are there really people who communicate by whistling?” and the answer is affirmitive. The Hmong are an ethnic group located in the East and Southeast Asia. They are a sub-group of the Miao people, and live mainly in Southern China, Vietnam and Laos.
The Hmong (Miao) claim an origin in the Yellow River region of China and according to linguist Martha Ratliff, there is linguistic evidence to suggest that they have occupied some of the same areas of southern China for at least the past 2,000 years.
The Hmong people whose territory is at the foothills of the Himalayas like most communities located in mountain areas, developed conversing through whistling to help farmers and shepherds communicate over long distances of up to 8 kilometers.
The Hmong language is one of the most musical languages in the world. The entire language can be whistled and communicated through musical notes which makes it one of the very few languages in the world that has evolved such a system.
The astonishing part is that these are not lyrics or songs but real words, and that makes the Hmong language quite unique.
Of the few that exist, most whistled languages are tonal and exist in Central America and Africa where majority of tonal languages exist. But there are also non-tonal languages that can be whistled. For example, in parts of Greece, and Spain in the Canary Islands.
Apart from aiding farmers to communicate across their fields, it also helps hunters to call to each in the forest while hunting for game. But their language is perhaps most beautifully expressed during a now rarely performed act of courtship, when boys wander through the nearby villages at nightfall, whistling their favourite poems between the houses and if a girl responds, the couple then start to date.
Source: https://guardian.ng/life/the-asian-tribe-where-they-interact-by-whistling/