If you've been singing along with Tim McGraw's hit "Southern Girl," you may have noticed a special effect that makes his voice sound "funky."

What is the special effect in Tim McGraw's southern voice song? According to Tim's record label, he used a vocoder.

What is a vocoder? According to Webster.com, a vocoder is an electronic mechanism that reduces speech signals to slowly varying signals transmittable over communication systems of limited frequency bandwidth.