Surprise surprise from Twenty One Pilots! We don't know if this is the first in a series or a one off but we'll take Twenty One Pilots music any way we can get it.
Tyler and Josh gave us a stripped down version of "Chlorine" from the Location Sessions. And if you put in the coordinates of 19.4326° N, 99.1332° W (which you can see by clicking this link), you'll see that it's in the center of Mexico City. Perhaps, on this North American Tour, they did a few acoustic recordings and will release more. Or maybe this is it.