AFTER making two albums using his Hexadic system of composition, the American folk and psych-rock pathfinder Ben Chasny retreats on Burning the Threshold to a familiar sector of the vast spectrum of outsider rock in which he is at ease. Rather than the frazzled jams of Comets on Fire, however, here we have the worship of open-tuned acoustic guitars, showcasing not, as did Hexadic, Chasny’s intellectual turbo, but the warm caress of callus upon steel string in dexterously strummed madrigals rooted in late 1960s US folk. While the music created under the Hexadic umbrella resembled nothing but itself, there are more linear echoes here of such acoustic godheads as John Fahey and Robbie Basho, with Chasny variously accompanied on guitar by Cooper Crain (Bitchin Bajas) and Ryley Walker. Indeed the latter’s playing with Chasny on Around the Axis is almost worthy of comparison to that of Bert Jansch and John Renbourn. Abetted by other guests including Damon and Naomi of Galaxie 500 and Trembling Bells’ Alex Neilson, this album is a more amiable affair than its immediate predecessors and a fine entry point for anyone unfamiliar with one of underground rock’s most enlightened musicians.