Mountains are a duo with a knack for the slow build. Air Museum, the sleek long-form album released by them in 2011, made a real case for the LP format - its strongest tracks were stronger in context than alone, its effects amplified by passing time.

With Centralia, Mountains have produced an album which hangs together in length while less in theme. Seven tracks long, it can be divided into two kinds of sound, alternating between the expansive (wonderfully present on Air Museum, and on 2009's Choral) and the immediate.

In a broad way, Centralia charts the usual Mountains territory: you can feel the album building, movement by movement (maybe moment by moment) in one wave. But it's a wave, this time, marked by distinct changes. For the first four tracks, Centralia follows that rough pattern: tracks one and three are a careful blend of sounds, while tracks two and four are lead by picked guitars.

For example 'Sand', the opening track, stands at around eleven minutes. Light and, in a strange way, tense, its subtle electronic sounds lead perfectly into the sharper acoustic guitar of 'Identical Ship', a track of three minutes. Around nine minutes into 'Sand', the almost-not-present panorama of sounds gives way to the first singular melody of Centralia: a beautiful, warm synth-string that's deep and cuts right into the track like a huge, relieved sigh.

The Air Museum approach to that effect would be to let it wash over the listener – to indulge that 'Ah!' moment for as long as possible. But 'Identical Ship' cuts that out, adding to it by taking it away; by making it longed-for in a not very distant past.

In that respect Centralia is more like Mountains' first LP Choral than Air Museum. If Air Museum was an exercise in one long sound, and Choral one in length, punched by interludes, then Centralia is Mountains showing their sound as a chopped-down-the-middle collection. While the first four of its seven tracks hold generally to that alternating pattern, the final three deal in both motifs at once, and work through them, internally, to their conclusions. The superb 'Liana', and 'Living Lens', which complete the album, are possibly Centralia's best tracks: but they stand alone, bolted on the end of the LP.

Still, Centralia is a Mountains album. Their music frequently has a filmic feeling about it - Air Museum could work as an alternative score to Blade Runner -- and the jangling wobble of 'Circular C', as well as the long, droning notes of 'Sand' and the sifting and sieving, shaky-crackle of 'Propeller', suggest a drive through open, bare country, the sun beating down on dry earth.

Centralia is earthier, in that way, than its predecessors. Choral, with its more organic-sounding stretches, sounded like the music to accompany the building of the glass city that Air Museum flies over and surveys; but Centralia is all about having an air to the ground, about driving over it. And while the sounds are a little different, that feeling that music creates images is what makes Centralia another characteristically "Mountains" album – and another good one, at that.