ArcTanGent Festival, a yearly outdoor four-day fixture at Fernhill Farm near Bristol, attracts a devoted following to its niche yet eclectic lineups of artists who generally have an association with post-rock, progressive metal, or experimental rock. It’s “sort of” a metal festival, but the range of acts it showcases steers towards the more left-field and eccentric end of heavy music and at times stretches beyond what could reasonably even be labelled as “rock”.