The importance of sound in horror movies cannot be underestimated. Arguably, it’s just as important (if not even more important) than the visual aspect of film-making. Try muting your TV and watching a scene you find ‘scary’. It just isn’t. However, it’s much more achievable to frighten people through sound alone. Loud noises make us jump. Screams and distress calls put us on high alert. And low frequency sounds can trigger an involuntary sense of unease and anxiety. The bear scream in Annihilation (2018). That Lawnmower scene in Sinister (2012). The death rattle in The Grudge (2004). You don’t need to witness these scenes to feel a chill. There is also something inherently disquieting about hearing a voice without seeing its source. Think of those unnerving real-life audio recordings of Anneliese Michel that inspired The Exorcism of Emily Rose (2005). Or the ‘seven days’ phone call in Ringu (1998). The popularity of podcasts and audiobooks has meant that a lot of us are regularly plugging in and enjoying audio ‘content’. So, we’re used to experiencing stories without any visual accompaniment too. That familiarity makes sound an even more powerful tool in horror, because we’ve trained ourselves to engage with it imaginatively. When there’s nothing to see, the brain compensates - constructing images, anticipating threats, and, more often than not, exaggerating them. What we think we hear becomes just as important as what is actually there. Pontypool (2008) and Hallow Road (2025) are films that utilise this to great effect.  And Ian Tuason’s undertone is the latest to get in on the act.

Evy (Nina Kiri) has moved back into her family home to care for her terminally ill mother, who is bedridden and barely conscious. She’s isolated but just about coping, in part thanks to the podcast that she co-hosts, which provides a welcome distraction from her real-life angst. This podcast is called The Undertone and involves her and her friend Justin discussing ‘all things creepy’ - paranormal experiences and reports from around the world. Although raised Catholic, Evy is the show’s sceptic and the pair record in the early hours of the morning because Justin is London based. And you know, it makes it all a bit creepier for the viewer watching her record podcasts at 3am in a darkened living room. Anyway, back to the plot. One day, Justin receives an email containing a seemingly random set of letters along with ten audio files. The files are recorded by a couple called Mike and Jessa and appear to be an attempt to record the latter talking in her sleep. At first the recordings just a little odd, but as they begin to work their way through them, they become increasingly disturbed. Evy starts to suffer mentally and begins to wonder if the odd events that have recently started occurring in her mother’s house are somehow connected to the audio recordings…

Director Ian Tuason shot undertone in his own childhood home. A place where he cared for both of his parents until the end of their lives. This poignant connection with the some of the central themes and the setup of the film are evident because although undertone is undoubtedly unnerving and chilling, it is also a sombre reflection on a wretched situation. One that both Tuason and his central character Evy, are forced to confront. Evy’s podcast co-host may provide the welcome presence of another human voice, but we never see him. And Evy’s mum is non-communicable, so Nina Kiri’s character effectively shoulders the burden of not just an unenviable situation within the story, but also being front and centre of the entire film. If she flops, so does the film. It’s a challenge she rises to and meets with subtle sincerity, however. Much of this film’s momentum stems from her reactions to things she hears (and sees) but despite an almost constant sense of ambiguity, Tuason thankfully never forces her into the role of unreliable narrator. When she listens to those audio clips, we’re right there with her.

undertone is careful in how it goes about building tension, almost to an insidious degree. It is happy to merely suggest that there are underlying horrors lurking within these audio files (and Evy’s own home) and is happy for us to let our minds run amok. When Evy listens to these clips and hears strange banging sounds, are they part of the audio or is it actually coming from inside her own house? When she replays snippets of children’s nursery rhymes backwards…is it just her imagination or does it sound like there are cryptic messages hidden within? When she hears a tap turning itself on upstairs, is it just bad plumbing or is her bed-ridden mother actually doing it? Or perhaps something else? (shudders) These uncanny moments indicate the potential of threat rather than confirm them and we live in this world for most of the film. And the result is a genuinely heavy atmosphere and increased anxiety levels. Tuason’s teasing use of negative space only adds to this.

The absence of conventional jump scares or moments of release allows tension to build to an almost unbearable level. However, Tuason ultimately opts to discharge this tension in a chaotic climax that feels more reminiscent of a polished supernatural thriller from the early 2000s than the restrained, slow-burn aesthetic associated with elevated A24-style productions. There are some images and visuals that border on the tropey right at the death and that’s a bit of a shame. For a work so meticulously constructed, the conclusion comes across as heavy-handed - perhaps even a touch contrived. While this does not undermine what precedes it, most of which is consistently compelling, it does result in a somewhat underwhelming final impression. That said, Tuason’s upcoming involvement with the next Paranormal Activity instalment feels like a perfect fit.