We've discussed here this before-- Hawaiian music, which was very popular in the first part of the twentieth century, uses falsetto leaps, and in a way that was very close to the way that it tends to be used in country/western music from the twenties, thirties, and forties.

The "Hawaiian Music Craze" swept the nation after the 1915 Panama-Pacific Exposition in San Francisco, and was fueled by scores of Hawaiian performers and instrumentalists who had come to the mainland after their Monarchy was overthrown. There were schools for music and dance set up all across the US, and much music was published and recorded--A lot of Hawaiian music was incorporated into American popular music--I haven't time to look things up now, but I recollect that some of the Yodelling Cowboys acknowledged listening to groups like Mme. Riviere's Hawaiians--