Naz Khanjani isn't a serial killer.

But when she infamously told a fellow The Bachelor NZ contestant that "all these girls are not here for Jordan", the audience could've been forgiven for thinking she was one step away from it.

As the reality TV star took her suspicions to bachelor Jordan Mauger, the musical score - ever present in most film and television, but especially so in the reality genre where it helps carry viewers through mundane real-life situations - turned haunting, with a hint of horror.

Then, as the intimate chit-chat came to an end with a cut to Khanjani - alone, in a different outfit and with no other context - miming firing a shotgun, it went full Psycho.

Actress Janet Leigh, as Marion Crane, in the famous shower scene from the film Psycho. Photo / Getty

In the Alfred Hitchcock classic, Janet Leigh's character Marion Crane is stabbed to death by a serial killer while taking a shower, a scene overlaid with a cinematic score so arresting it's become synonymous with horror in the six decades since.

But Khanjani wasn't dispatching her love-seeking rivals to the tar pits - Crane's ultimate fate. She was just throwing a bit of shade.

Cue shrill music an inch away from the screeching violins, violas and cellos so well-known from the master of suspense's biggest hit.

Khanjani remembers watching the scene, and others in the show, where "they made the music sound so scary or evil when I was on TV".

"I was genuinely trying to warn Jordan because I'd seen what was going on when the cameras were away, but they add the music to it, they add the editing to it and it just got a whole lot worse … it definitely changed the public's perception. It just makes it so much more dramatic.

"You're not [aware of the score] but it does actually have an impact. I know because even me watching it, knowing how it all ends, I found that it sort of changed the mood for me as well."

Naz Khanjani wasn't always impressed with the musical score used during her scenes on season two of The Bachelor NZ. File photo / Norrie Montgomery

Khanjani's experience is no surprise to reality TV expert Dr Rosemary Overell, a longtime fan of the genre, who has tapped into its influences as part of her University of Otago academic career.

"Even though Psycho is a film made beyond yours and my generation everybody knows that theme. It's part of our cultural imaginary, so obviously the association of that music with that contestant implies that she's a psycho, the other girls think she's a psycho."

A crescendo of ear-piercing string instruments helps our minds form a conclusion about what we're seeing because we're conditioned to associate it with certain outcomes, Overell says.

"It depends on having those cultural reference points which we would almost unconsciously not even really think about."

'If you're aware of the music, it's not doing its job'

So, what Khanjani heard as she watched herself on screen is nothing new.

Actually it's really old - much older than a snarky romance reality TV show or even a black and white classic made two generations ago.

A well-composed score giving the storytelling a nudge dates to before the invention of film itself.

In fact, according to musicologist Dr Gregory Camp, it's hard to say exactly when the practice began, because people always draw from previous traditions.

Dr Gregory Camp, from the University of Auckland, is a musicologist. Photo / Supplied

Musical scores were influencing audiences well before moving pictures morphed from novelty to the multibillion-dollar mass entertainments they are today.

"Going back to the very beginning of the history of film music, before there was any dialogue in the films - because they hadn't figured out how to technically sync it up yet - music was used as a primary mode of communication, and that connects into the earlier history of opera and ballet."

Takapuna composer Marshall Smith has been composing music for film, TV, computer games, talking books and businesses for more than a decade.

He and The Sound Room business partner Tom Fox have approached reality TV production companies, but have been told the shows use production library music.

"Bespoke music for reality TV would be rare. Maybe Grand Designs, MasterChef. It depends on how big the brand is, The Bachelorette [franchise] is massive; they probably have existing content."

Whatever the project, the score almost always reflects the director's vision. Usually, a final cut of the film or show will arrive, sometimes with a reference track containing other movies' music as a guide, or with notes marking where the score needs to reflect a particular emotion.

"We have a bit of a language so if they say we want it big, we know what they mean, or if they say they want it intimate, we know.

Marshall Smith, managing director of the Sound Room. Photo / Michael Craig

"So often the music is working in contrast … if you're aware of the music it's not doing its job very well. You're there to support the action on screen, not to get in the way of it."

Smith is used to people not quite understanding his job.

"When somebody says, 'What do you do?' and I say, 'I write music for TV' and they'll go, 'What do you mean?' I say, 'Well, you know all those programmes you watch? There's music all through them' and they go, 'Oh, right'."

The villain, the hero, the lover, the fighter

Reality TV is "literally colour-by-numbers", Smith says - pulses for tension; warm, gentle orchestral music for romance.

"It says, 'Oh, it's a romantic moment', 'Something thoughtful's happening here', 'tension', 'drama'.

"I think people come home from work and want to switch off, and music helps to do half the work for you."

Camp is in no doubt about the impact of a score - from the biggest film blockbuster to the cheapest reality TV offering - on the audience.

"It has a huge influence. The music ... tells us what the visual might not tell us, about who's supposed to be seen as the villain, who's the hero, who's the lover, who's the fighter, because over the years we've developed a series of codes.

"So the low double bass note means impending doom or the high violin means romance. Composers can use those tropes, those expectations to really quickly to tell us what to feel about the characters or the situation."

The Jaws score is a famous example of low double bass being used to signal impending doom. File image / Supplied

And don't expect big differences between fictional and reality TV scores, they're similar, and that's the point.

"The idea is to make what we're seeing as reality [TV] just as engaging as a scripted drama or comedy."

So, if you taped everyone's mouth shut, could you follow the story with just visuals and music? Probably, Camp says.

"Especially in reality TV, a lot of the playing time is accompanied by music."

How it's done

The Herald on Sunday put Camp's comment to the test by watching The Bachelorette NZ's 90-minute opening episode with the University of Auckland academic.

Camp passed - the music, and with it the cliches - barely stopped, starting with "really simple, mostly three-chord" repeat patterns of solo guitar helping introduce bachelorette Lesina Nakhid-Schuster.

"They're presenting this view of her as down to earth, because obviously the audience is supposed to identify with her," Camp says.

Cocky suitor Liam Cochrane, by contrast, arrives on screen to electric guitar, while hapless Brendon Vanstone, ditched in the first week, has his opening verbal flub musically scored.

Electric guitar was used as the background music when confident The Bachelorette NZ suitor Liam Cochrane was introduced on screen. Photo / Supplied

The contestants can expect plenty more of that; unlike fictional drama or comedy, reality TV would be "pretty boring" without musical accompaniment, Camp says.

"You'd just be watching awkward people being awkward. Adding the music either makes it into comedy, or hides it, and keeps the flow going."

Several other cliches find their way into the score, including the use of semitones, the smallest interval in Western music, as the bachelors vie for top-dog status.

The most dramatic music is saved for the rose ceremony, when Nakhid-Schuster decides which of her suitors will stay.

The superhero-movie style music tells the viewer "this is really important", Camp says.

"[Composer] Hans Zimmer is the big influence. It's what I call the 'Hans Zimmer chugga-chugga' [style] … it gives a sense of forward motion."

The superhero-movie style score told viewers Lesina Nakhid-Schuster's rose ceremony in The Bachelorette NZ "is really important", music expert says. Photo / TVNZ / Matt Klitscher

But not everyone gets a rose.

"Oh, sad piano music," Camp says, as three suitors are sent packing.

He's not a Bachelorette NZ fan, but can appreciate the craft that has gone into scoring the show.

"As cliched as it is, you have to know what the cliches are, in order to follow them and to keep enough interest that you keep watching it for an hour and a half."

And that's given, in most of the reality shows he's seen, the score "isn't really meant to be noticeable".

"It's more there as an undercurrent telling us quietly what to think. and how to feel about the scene."

The fastest sense

So how can we be influenced by the music we're hearing, but not realise it?

It's thanks to our rather nimble auditory system.

Not only does it never take a break, it's also busy filtering different auditory streams, says hearing researcher Dr David Welch.

"So while we might be consciously attending to the main action of a TV programme there will be parts of our brain monitoring the background music and those cues from the music will be made available to our brains … and it will activate other areas of the brain that know what this tune is.

"When you recognise something you activate in your brain a whole network of associations … that [can] colour your experience of the main action."

Our auditory system is quite amazing, hearing researcher Dr David Welch says. Photo / Supplied

Hearing is also our fastest sense, likely evolving as a warning signal for distant ancestors who couldn't turn on a torch to see predators in the dark.

Our auditory system recognises sound in 0.05 seconds, compared to the at least a quarter of a second it takes the brain to process visual recognition, American auditory neuroscientist Seth Horowitz told US media Radiolab.

Our brain also senses changes of sound occurring in less than a millionth of a second, Horowitz told Radiolab.

It's all very clever, but not necessarily fair.

For example, in the past some American reality shows would often use hip-hop music when focusing on black contestants, but that's changing, Overell says.

University of Otago lecturer Rosemary Overell is an expert in reality TV. Photo / File

She hasn't noticed any difference between how male and female reality TV contestants are treated by the show's scores.

"It would be something to think about: how particular contestants might become associated with particular little muzaks or [musical] motifs. In the past 10 years the media industry has become more aware of things like sexism and racism."

If it does happen, Overell says, the contestants may not even be aware themselves, which is why it's important to "pause, think about it … and unpack those things we don't even notice.

"Because those are often the very things that produce uneven power relations. It's kind of insidious. But the reason we don't notice them is because we know them so well, so without even doing much thinking we would collapse Naz with [the killer in Psycho], which is kind of a crazy thing to collapse.

"But that little hook of music puts that association there."

Keep an open mind while watching reality TV shows, The Bachelor NZ season two contestant Naz Khanjani says. Photo / Norrie Montgomery

Khanjani knows the sort of music she'd rather have heard as the scene was broadcast to the country - something soft, to reflect what she was doing.

"They should've made me look like the nice person trying to warn Jordan, but they made it completely opposite by mixing that music in, by showing certain bits. I hate to say it, they made a really good job of making me look bad."

She has a simple message for viewers of a TV genre she was once hooked on, but now avoids.

Have a giggle, but also keep what reality TV shows in perspective - you might not be seeing, and hearing, what you think you are.

"Just be a bit more open-minded."