Flanging

She had one more Top 40 hit in 1962, a song about the Berlin Wall called West of the Wall, but The Big Hurt is the record she's remembered for.

Notice I said record and not song, because The Big Hurt as a song is fine, if nothing extraordinary, and a little old-fashioned, but The Big Hurt as a record is another matter because it is the first hit record to feature flanging.

Flanging, to put it as simply as I can, is an effect created when two copies of the same audio signal are played simultaneously but slightly out of sync.

And if they're out of sync by more than 20 milliseconds or so, you start to get an audible echo effect.

You can hear that there are two.