DJ Fortify has made multiple tracks and has the most popular PewDiePie song. The song is called 'Chairmode Activate' and has had over 12 million hits. The video also has montages of various PewDiePie fanarts. He has created songs for various other YouTubers and likes to use dubstep in his creations.
You can listen to the song below or download from here (right click the link the save as a .mp3 file)
DJ Fortify's music can able be streamed and downloaded free from his SoundCloud page here: https://soundcloud.com/dj-fortify
DJ Fortifys YouTube Channel: http://www.youtube.com/user/Hadermaner