The lonely goatherd, in a "Sound of Music" song

• Old-time country singer, sometimes
• Producer of high and outside pitches?
• Alpine caller
• Alpine singer, perhaps
• Jimmie Rodgers or Tex Owens, musically
• Alpine warbler
• One making frequent pitching changes?
• Person who sings like someone in the Swiss Alps
• Alpine vocalist

Wiktionary Word definitions in Wiktionary
n. One who sings so that their voice fluctuates rapidly between their normal chest voice and a falsetto, one who yodels.