Exo is a special sort of album. It's not the kind of listen that's going to be for everyone, and can be quite overwhelming at times, but that same divisiveness is part of its appeal. Some albums are merely heard; some have an almost physical presence, and so are felt; Exo fits into neither of these categories - it is an album so involving that is not heard or felt so much as experienced. Opening track 'IMAX' stands out from, and paradoxically gets completely swallowed up by, the rest of the album, because it is the sound of Aaron David Ross and Matthew Arkell, a duo collectively known as Gatekeeper, at their most serene. There are of course moments of respite further down the line - they're entirely more creative than contemporaries who, with an album like this, would seek to pummel the listener over the head for 35 minutes, non-stop.

Designed to work as one flowing piece from start to finish, there is that non-stop element to Exo, but its peaks and troughs are what's most important about it. It's such an intense and immersive experience that, no matter what, the listener feels like they've been chewed up and spat out by the album's forceful nature by the time the triumphant, choral (yes, choral) send-off of 'Encarta' comes to a halt, but there's enough variety in there to keep them coming back for more. 'Tree Drum's' gently flowing melody is underpinned by suitably powerful percussion, but its atmospheric intro is merely the calm before the storm, as it is later obliterated by a percussive cataclysm that brings any false sense of calm to an abrupt halt. The album rattles along with little thought for those who have to keep up with it, packing multiple parts into each separate track, a trick which is most notable on 'Hydrus', which shuffles along for a minute and a half before opening out into a cinematic sprawl of sound.

There are times when such nuances are entirely forsaken; 'Exolift' features a formidable 4/4 bass drum thud, its brisk tempo sweeping things along as different melody lines disappear and reappear almost at will, yet always sounding impressively driven and focused. It's hard to be sure where one song ends and another begins, such is the album's flow, but it is quite telling that not even once does Exo sound like it's lost its way. At times, its sole purpose is to take one's breath away, but this intricate album is so much more than them sum of its parts, creating its own, high-energy, high-speed world and sounding better with each passing listen. At its heart lies another contradiction - its greatest strength will be seen by some as its biggest flaw - but this makes it all the more compelling.