Yodeling
Yodeling is widely believed to have originated in the Swiss Alps as a means of communicating over large distances. A yodel can communicate from mountain to mountain, especially when aided by echoes, much more effectively than shouting. References to yodeling date back as early as 1545.
A singer who is yodeling will sing one note to make his or her tune but will add variation to it so that it goes up and down in tone and sound from low to high and so on. This singing technique showcases the two main ways of singing from the head and the chest at the same time.
Despite having originated as a means of communication, yodeling has seen favor by many musicians over the years.
From a music perspective yodeling also plays a major part in the musical cultures of many other countries. In Europe, for example, yodeling can also be heard in some traditional Georgian music. It is also a primary part of many traditional Pygmy songs in Africa. In the USA many country and western singers have also incorporated yodeling into their songs. This may simply be a decision made by the song writer or it may be based on traditional yodeling in musical genres such as bluegrass, for example.
Perhaps the most famous was The Singing Brakeman, Jimmie Rodgers with his trademark Blue Yodel sound in the twenties and thirties.