It’s hard to describe Non Opus Dei’s style, as although clearly rooted in both Death and Black Metal there’s an experimentalist mindset at work here that defies categorisation. As well as being technical, progressive, and atmospheric, there’s a twisted feel to the music that makes it all the weirder. It’s far too complex to try and sum up, but a mixture of Emperor and Behemoth, each at their most experimental, comes fairly close, although Non Opus Dei is original, having its own style.

Clearly a highly skilled group of musicians, these Poles are capable of creating a dense, dark atmosphere without sacrificing the technical side of the music, surprisingly rare even nowadays. Much of what makes this album so good is the unusual drum patterns, such as in Alne, providing more of an interesting listen than music of this sort generally does. Of course, the guitarists are excellent too, producing some wonderfully odd riffs that are the focus of most of the songs.

Beauty kicks the album off in style, heavy riffs battering you before sudden spoken vocals and a mounting swirl of Proggy riffs completely change the focus. Ona Jest Kluczem follows, a mid-paced groove of riffs and technical drumwork, made all the more mysterious by the Polish lyrics, spoken and snarled. Other highlights are the oddly titled 23.09.2006, which is especially complex, and penultimate song Saule’s Journey, which is Thrashier, sounding like Progressive Aussies Alchemist on a very bad day.

Constant Flow is one of those albums that were a better-known band to produce it, it would be hailed as a masterpiece, but as Non Opus Dei is yet to get ‘there’ odds are that it will pass unnoticed, which is a great pity as there’s much of worth here. As with most things, there’s room for improvement – remixes stopped being interesting about ten years ago, so why modern bands feel the need to clumsily slather one of their songs in electronics as a ‘bonus’ track is beyond this reviewer. Still, Non Opus Dei don’t make a complete hash of it, and it ends the album well enough. Ultimately, this is a unique take on Blackened Death Metal that will last a long time on the playlist if you take the plunge.