Frank Ifield a folk singer ????

There is a complete CD given over to yodelers in various styles currently available which you should be able to find at any worthwhile specialist store.
I personally would try County Sales mail order at Floyd, Virginia, they are on the web.

Someone above mentions Bill Monroe's version of Muleskinner Blues. This song of course originates from Jimmie Rodgers the singing brakeman who inserted a yodel into almost every song.

Personally although I'm guilty of the crime from time to time I agree with John Lily's song "A Little Yodel goes a Long Long Way"

Good luck and don't scare the dog.