Music makes cows happy, and the happier the cow the more milk they produce. So this is your chance to create a song (with some loops, a la garageband) that will be judged by the heifers themselves. if the cows like your song, you win a trip to the Grammy's.
Videos of the cows reacting to the song will go up on November 7th, with the final winner announced November 26th.
Fun idea. And kind of cool knowing you are in one way contributing to the well being of the cows producing your milk. But the usability of the site is frustrating as you can't play along to your recorded tracks when you add new ones. So it's a bit of guess work involved. Maybe that's why they have an "autosong," that creates a version for you.
By the way, science backs up the Cows Love Music theory, too. So it's not just a gimmick.
In fact, other ad shops have tapped into this. Jung von Matt played on a similar farm (geddit) last year with this spot in which they create awareness for Konzerthaus Dortmund by selling milk from cows who listened to the orchestra.
It makes me want to go to a local farm with a bangin' playlist and see what cows really like. My guess is, it ain't dubstep.