CHVRCHES - Tether (Instrumental)
from the instrumental version of the album, as far as i know they are the official instrumentals.
the official page with samples of the instrumental version: http://www.umusicpub.de/de-DE/Digital...
not sure where to get the full instrumentals anymore. it was available if you searched google for: "bones of what you believe instrumental" (with and without quotes) but those links were taken down