that country music "ay"

Are you familiar with the phenomenon of Sacred Harp singing? It's like a cross between a quilting bee and bagpiping, but sung.

This right here is a 1958 recording of Sacred Harp singers from Okeefenokee region of SE Georgia and NE Florida. If you can stand to get through it enough to get past the syllables and into the lyrics, you'll hear them clearly pronounce diadem "die-ay-dem," thus showing that the country pop music practice of substituting an "ay" for a schwa is well-grounded in one of the source regions for that music.

Wɛiɛl ɐ'll be ɛi monkey's uncle.