I'm stealing this comment from Youtube that summed up how this performance might have been received at the time it was recorded in 1958:
"The softspoken recitation before this sells everything perfectly. Imagine you are about to hear this in person for the very first time. A quiet shy brunette with a plain guitar strolls onto stage with her backup band in The Fifties. And becomes The Queen Of Rockabilly from the first tumultuous note that she sings."