Rarely has there been such a gaping disparity between how little a band promise on paper and their actual earth-battering prowess. Essentially, Arbouretum specialise in strictly un-ironic psychedelic boogie. Imagine riff-repeater chiefs Endless Boogie without the knowing smirk, or Gandalf-metal practitioners Dead Meadow with a vastly superior singer, and you’re not far off the Baltimore quartet’s signature sound.

All of which might sound distinctly off-putting; stoner-rock taken to the ludicrous extremes where the heavy-lidded musicians have lost all sense of just how daft their single-minded devotion to heroically extended fretboard explorations and lyrics dabbling in various mythical/mystical themes might seem to uninitiated.

But – and this is one supersized but – it’s precisely this unswerving devotion to unfashionably musty templates and grabbing hold of every opportunity to go proudly epic that makes Arbouretum’s fourth album such a colossally potent triumph. By steadfastly refusing to recognise that there’s anything even remotely funny and/or embarrassing about virtually endless tunes about marching bands of warriors and such that consist largely of fuzzed-out guitar solos, the four-piece present a powerful case in defence of rocking out with the most mind-expanding means possible, the reserves for which have lain largely untapped since the glory days of Black Sabbath – the most audible influence here, alongside vintage British folk-rock (especially Richard Thompson) – and various lesser vintage sludge-cookers.

Strong as the other tracks are (only the brief and bouncy ‘Empty Shell’ fails to fully convince), the mighty closer ‘Song of the Nile’s the best point of entry. Over a generous ten-minutes plus duration, band leader Dave Heumann maintains a startling cavalcade of guitar heroics, reaching an intensity wherein the searing sounds emerging from the most likely overheating amps resemble the dying squeals of some prehistoric beast, breaking occasionally to deliver a verse about “wondering down in Egypt” in an expressive, booming baritone whilst the rest of the band cook up a compellingly primitive groove.

Whereas on earlier Arbouretum albums the tunes have occasionally come across as little more than loosely assembled frames to hang those extended bouts of amp abuse on, the melodies throughout ‘The Gathering’ are uniformly strong. And just in case the emphasis on musical muscle-flexing becomes a bit overbearing, a sparse take on ‘The Highwayman’, Jimmy Webb’s brilliant ballad of a time-travelling shape-shifter, proves Arbouretum handle stark beauty just as well as they do epic grandiosity.