The yodelling sound happens when a singer's voice breaks — on purpose. The jump from a low note to a very high note creates a crack or flip in the voice. Most people try to avoid this in everyday singing, but yodellers train to do it deliberately and rapidly, giving the song its bouncing, leaping quality.
In the Austrian Alps, yodelling was originally practical as well as musical. Mountain farmers used it to call cattle, communicate with people in distant valleys, or signal their location in foggy weather. The Alps create natural echoes, so a well-placed yodel could travel several kilometres.
Today yodelling is performed at folk music festivals, competitions and concerts across Austria and the wider Alpine region. There are competitions where singers are judged on the clarity of their voice breaks, their rhythm and the beauty of their tone. The best yodellers can switch between voices dozens of times in a single song.
Yodelling in various forms exists in cultures around the world — from Swiss mountain traditions to African pygmy music to American country music (which borrowed vocal flip techniques from Alpine immigrants). Austria's tradition remains one of the most celebrated forms, closely tied to Tracht (traditional costume) and alpine folk culture.