Ethnomusicology, the study of the musical traditions of isolated communities or those on the verge of extinction, is an exciting… and potentially dangerous practice. At least, it is for the young couple at the center of this strange folk horror, when they find an ancestral song with the power to unleash an evil that originated in another era. With echoes of the earlier films directed by Ben Wheatley and Peter Strickland, this is one of the most unique and unsettling releases of the year.