The legendary Swedish rock band has morphed and disappeared and returned several times since 1969. Their 2018 incarnation is called Träden, a four-piece featuring only one of the original members. This (mostly) instrumental guitar rock is very clearly built from group improvisation. The band’s love of equilibrium and equity comes through here, where a solid, ecstatic mood prevails for over an hour. Modest at first, these rugged spiritual jams stick to your ribs and warm up the room.