Cow- and goatherds used yodeling as a way to call across from one mountain to another. It was a rudimentary (albeit beautiful) way to communicate. Certain sounds and notes actually meant words, so in a way, yodeling began as a kind of melodic language of the mountains.
Although you couldn’t see a fellow cowherd across the valley, you could hear him, and you would yodel back. Like bird calls, sending out feelers to see who’s out there and listening to the responding calls that come back.
I like to think how long before two teenagers picked up their phones and started texting one another, one would stand tall on a rock on some mountainside and yodel some little phrase across the valley to the other, who would yodel back.
Read a lot more about yodeling in Switzerland at National Geographic's Intelligent Travel blog. Link -Thanks, Marilyn!