This morning Katy Perry released information that there are disco ball hidden all over the world in popular cities in which you can listen to a teaser of "Chained to the Rhythm". Check out the map if there is a disco ball near you. (OP went to the disco ball that was hidden in Chicago. OP's PROOF.)
What you will hear if you go find a disco ball is the chorus and the bridge for the song. It's very loud once you plug in your head phones. Here is a snippet of it that is floating around and it keeps getting taken down on Twitter.
What do you think ONTD?
SOURCE: 1, 2