Movies about outer space and aliens have been a cinema staple since the dawn of Hollywood. It takes something special to liven up the genre and 2013's Under The Skin was an incredibly special piece of cinema from genius director Jonathan Glazer. The film took over 10 years to come to fruition, but the wait was worth it, as every element is polished to perfection including the unnerving soundtrack.

Stripped down from Michel Faber's novel, the film follows Scarlett Johansson's unnamed alien character as she crawls the streets of Glasgow in a white transit van picked up unsuspecting men and leading them to a stylised demise. Booed at its Venice premiere, lauded by the Guardian and loathed by the Indy, Under The Skin is a polarising masterpiece of the Terrence Malick slow-burning ilk.

According to Glazer in a Film4 interview, they "wanted to stay away from alien...stuff" like futuristic technology and cliched alien appearances. His key definition of Under The Skin was that it should be 'unadorned' - this philosophy initially led the producers to the conclusion that the film shouldn't have any music until a human introduces the alien to a record. This in itself led Glazer and his team down a cul-de-sac because of the statement and importance of what that record would be. This found Glazer with nothing more than an idea, a mood, a feeling that "the aliens are coming." It was a complete film novice in Mica Levi that stepped up to capture and realise this idea.

Glazer himself has musical pedigree having directed numerous iconic music videos (Radiohead's 'Karma Police') as well as era-defining TV ads (Guinness - 'Surfers'). It's only fitting that he should choose a boundary-pushing artist like Mica Levi to score his long-gestating film. Levi is most notable for being a part of the group Micachu and the Shapes but this is only scraping the surface of her talents. She is classically trained in viola, a former artist in residence at the Southbank Centre and a former student of the Guildhall School of Music where she studied music from a variety of composers including the incredibly challenging Xenakis (give it a go if you're feeling adventurous).

Her score for Under The Skin is noted for its nods to those composers, whose music has soundtracked some of cinema's most unsettling moments: György Ligeti (2001: A Space Odyssey), Krzysztof Penderecki (The Shining) and Bernard Hermann (Psycho). Levi's score has been BAFTA nominated and called "definitely the worst score I have ever heard" - surely the mark of something truly special.

The film opens with the genesis of the 'alien' and the first rumblings of Levi's unsettling score. The Pitchfork review of the OST puts it beautifully: "The score opens with a locust plague of dry tremolos, the strings pressing down until the sound has reached a roar." The viewer is immediately displaced and transported to a Shining-like situation where all feelings of security are discarded.

The use of strings is a constant in the film. This was a conscious effort by Levi as Glazer was keen for the score to be performed live and not to become obsessed with the infinite nature of electronic composition. A three-note motif recurs throughout the film, Levi describes the relationship between the alien and the musical motif:

"She uses that theme - it's her tool. At the beginning, it's like fake - it's her perfume, it's the way she reels in these guys with a tune. Then it deteriorates, it becomes sadder. We called it the 'capture' melody. Then there's this major triad, a warm chord, and that's her 'human' or 'love' feeling. And there's this darker minor triad of trilled strings that recurs throughout."

The deterioration of the theme is a fantastic way of portraying the alien's changing emotions towards her murderous mission. The visual effect of Scarlett Johansson luring her victims into an inky black void is nothing short of breathtaking and the accompanying drawn-out strings and knocking drums are mesmeric.

The film's departure from the three-note motif comes in the 'sex' scene with the unassuming man who took the alien into his home thinking she was in trouble. After a day of showing her the sights and offering her food, the man's intentions grow clear and the soundtrack moves closer towards Vangelis' Blade Runner score than the previous Kubrickian influences. Levi describes this process as: "looking at the natural sound of an instrument [and] trying to find something identifiably human in it, then slowing things down or changing the pitch of it to make it feel uncomfortable. There was a lot of talk of perverting material. It does sound creepy, but we were going for sexy." The scene itself is unnerving in its length, and would be a totally different proposition in silence (or with steamy '70s sax sex scene music).

The film reaches its terrifying and brutal conclusion in a snowy highland forest. Again, the film's visuals by Daniel Landin are stunningly beautiful. The three-note motif has slowed and decayed until it almost falls apart. At this final point in the film, it's clear that the power of Mica Levi's music comes not only from its haunting composition but from the scarcity of any other sounds present. Scarlett Johansson's alien is almost nothing more than a silent mirror to the world she has landed in and the extended periods of nothingness build tension further and further. "As the film moves along, there's more silence because there's fewer narrative reasons for using music," claims Glazer. "It becomes about embracing the real sounds of the world: rain, wind, and everything else that she's starting to experience."

The sound of snowfall following the screeching strings is a true masterstroke, and in the film's final moments it epitomises the sheer artistry involved. If it takes another 10 years for Glazer to make a film or for Levi to score a film then it will have been a worthwhile wait.