For their sixth album, Long Distance Calling are going back to basics. The German post-rockers began as an instrumental outfit, dabbling with guest vocals and only introducing full-time singers on their last two albums. With Boundless, everything’s stripped back to the initial formula – all instrumentals, no guests, no vocals. The difference is that by now the quartet are experts in texture, tone and atmosphere, eschewing the post-metal tropes of loud/quiet dynamics. The majority of tracks are left to their own devices, steadily building to vertiginous peaks of thundering noise and vortexes of melody. Consequently, there’s a lawless feel to Skydivers and Ascending, the latter opening with Mastodon-esqueriffery before overcast ambience takes it to a dark, dramatic place. Boundless might revisit LDC’s roots, but it’s less a step backward, more a cinematic homecoming.