It's SOMEBODY THAT I USED TO KNOW by Gotye, a Belgian singer/songwriter who wrote this to lyrically capture the experiences he has had with relationships. The song was released on July 2011, rose to critical acclaim & a surprising success in Australia, became #1on the music charts in mid-April 2012 in many countries, particularly in Australia, New Zealand, Belgium, the United Kingdom, the Netherlands, Germany, Austria, Ireland, Denmark, and the USA. As of April this year, 4.5 million copies had been sold worldwide according to Universal Republic.
It has become so popular that many versions of the song have come up:
in AMERICAN IDOL