Are you referring to a yodeler?

Yodeling (or yodelling, jodeling) is a form of singing that involves singing an extended note which rapidly and repeatedly changes in pitch from the vocal chest register (or “chest voice”) to the head register (or “head voice”), making a high-low-high-low sound. This vocal technique is used in many cultures throughout the world.

In Swiss folk music, it was probably developed in the Swiss and Austrian Alps as a method of communication between mountain peaks, and it later became a part of the traditional music of the region. In Persian and Azeri classical music, singers frequently use tahrir, a yodeling technique that oscillates on neighbor tones. In Georgian traditional music, yodelling takes the form of krimanchuli technique. In Central Africa, Pygmy singers use yodels within their elaborate polyphonic singing. Yodeling is often used in American bluegrass and country music.