You know the old saying "There's more than one way to skin a cat" well there's more than one way to call for a hog too. In fact, there's a whole art to it and rural America is perhaps the world's leading exponent.
As can be witnessed in this prime piece of footage from the 2010 Illinois State Fair's hog calling contest which, according to the text accompanying the video on YouTube, was won by Kyle Barton of Des Moines, Iowa.
It also goes on to say "This is his first win at the Illinois State Fair, although he's claimed the title at the Iowa State Fair before and plans to hit a few more states with his hog call." Let's hope he did that. Btw, Kyle also went on to win Illinois' contest in 2011 and 2013. So well done to him.
Hog calling is practiced by pig farmers and contests are held at state fairs in places known for pig raising. Contestants have to imitate the sounds of hogs and are rated on their abilities by a panel of judges. Criteria judges look for are loudness, clarity, and creativity (the woman below gets an A+ from me on that), according to this article by eHow.
So now you know.