Grouper's 2008 record Dragging A Dead Deer Up A Hill, buried in pedal effects and infused with melodies that crept like wisteria, found itself welcomed with open arms by those weaned on the psych-folk drones of Animal Collective, Pocahaunted, Fursaxa et al. AIA sees Liz Harris return with two self-released LPs, Alien Observer and Dream Loss, and, rather than continuing to explore the subaquatic singer-songwriter sounds of that breakthrough album, she has elected to scurry back to the subterranean droning of earlier works such as Wide and Way Their Crept. With a clutch of ethereal, feminine dream pop releases in recent months from the likes of Julianna Barwick, Silver Pines and Sleep ∞ Over she has plenty of competition, but AIA, essentially a double album, cements her place as leader of the pack. Harris has always outfoxed her peers in terms of pure atmosphere, and these twin 12”s are no exception.

From the moment Alien Observer's 'Moon Is Sharp' rises from the speaker like mist from a mountain lake, we're drawn back into her immediately identifiable soundworld; she can still conjure the experience of teetering on the precipice between consciousness and slumber like no other. Yet instantaneously, the sonic shift from Dragging a Dead Deer… is apparent; where that album's reverberating was tempered by its acoustic elements like sunbeams through rain, here we find ourselves in far darker, deeper terrain. Prettiness has expired in favour of unsettling ambience carved mainly from a minimalistic combination of tape loops and otherworldly electric piano – instrumentation that allows her somnambulant soundscapes to become even more atonic.

That said, the stripped-down despondency of her aesthetic choice does sometimes mean that her bucolic psychedelia seems more earthy, more grounded. Her last record was reminiscent of ancient rural landscapes, the wintry, rainy New England backwoods that HP Lovecraft found horror in. Here the spookiness is still redolent of the realm of that writer, but is more of a cosmic variety. 'Alien Observer', sees Harris conspicuously exposed, a simple, undulating keyboard melody with those unmistakable, umbrageous vocal tones hovering over the top. It's one of the most tangible songs she's released, the mist clearing to reveal a tautly written, almost accessible pop song. Its lyrics - for once fully discernable - seem rather trite, ripe with sci-fi cliché, tying in with its cheesy promo video.

Somehow that makes it all the more wonderful; its b-movie imagery suggestive of queer-coloured lights through the trees, and tying Harris into the tradition of the primitive electronic weirdness of Delia Derbyshire and the BBC Radiophonic Workshop. You half-expect to hear a Theremin spiraling out of the murk. If past Grouper releases have inhabited abyssal trenches and damp backwoods, here Harris takes us journeying across constellations and stars. It's relaxing and somnolent, yet there are undercurrents of uneasiness running through both the records. 'Mary, On The Wall (Second Heart Tone)', wakes the listener from the Alien Observer record's hypnotic trance with its clanging intro, a child's music-box amplified to uncanny levels. Likewise, Dream Loss's 'I Saw A Ray' abandons melody for an industrial pool of surging fuzz, and 'Soul Eraser' lives up to its title, an amniotic drone that exists purely to feed the imagination.

More than any other ambient project of its ilk, Harris's music serves to summon visions and act suggestively, filmic in its scope. That scope is reflected in the foolhardy ambition of making a double album, and, although it might seem extremely inadvisable for a lo-fi dream pop musician to attempt such a project, Harris has to be credited for (almost) pulling it off. Dream Loss is certainly inferior to Alien Observer, and there's no denying that a combined listen of the two together causes the records to lose some of their power through the repetitive nature of the music. Yet imbibed separately, they're two of the most beguiling albums of the year, exquisitely realised and singularly evocative. Harris has effortlessly shown that, amongst a growing clique of ladies making lenitive psychedelia, she can take us on the most arresting trips of all.