Have you watched a horror movie so terrifying you had to look away and mute the TV at the same time? Sometimes, the most frightening part of horror isn’t what we see. It’s what we hear.

Music is a vital feature of horror movies and TV shows because it elicits emotional responses and adds an unspoken undertone that can completely change a scene’s meaning. In fact, music has a psychological effect on human brains.

According to an article from Harvard Medicine, autonomic nervous systems, which control heart rate and breathing, are directly affected by the tone of the music and an individual’s response to acoustic cues.

Music directly affects the brain’s responses and, in turn, people’s emotions. There are many examples of music’s effect in today’s popular horror media.

For instance, the award-winning sci-fi horror Netflix show, “Stranger Things.” The instrumental synth background music emphasizes the unnerving retro-horror plot. In particular, the repetitive beat, which resembles the sound of a heartbeat, sets the tone of danger lurking, therefore building suspense.

The eeriness of “Stranger Things” is also created by songs with lyrics that accompany key moments in the show. In the third season, Vera Lynn’s 1939 song, “We’ll Meet Again,” plays into a major plot twist that altered the course of the season.

In the historical context of when it was released, the voice of “We’ll Meet Again” is singing to a loved one who is away at war. The narrator is saying goodbye to this person with the hope they will meet them again someday.

Although “We’ll Meet Again” is, at its core, an endearing song, in “Stranger Things,” the lyrics, along with horrific imagery of the scene while it plays, transform the song into a haunting one.

Additionally, in the final season of “Stranger Things,” the 1954 song by The Chordettes, “Mr. Sandman,” is also used to convey a feeling that is opposite of what was originally intended.

The narrator of this song asks someone called Mr. Sandman for a lover because they are lonely. The core message of the song is that the speaker wants Mr. Sandman to deliver their dream man.

Comparatively, in “Stranger Things,” Holly Wheeler, a young girl who is lonely because she is isolated at school, becomes friends with a man who calls himself Mr. Whatsit. When Mr. Whatsit’s true identity is exposed, “Mr. Sandman” plays in the background.

Holly Wheeler wanted friends, just as the narrator of “Mr. Sandman” wanted a lover. However, the “friend” that was brought to her was revealed to have a sinister ulterior motive. Therefore, playing “Mr. Sandman” during the pivotal identity reveal gives the scene an unsettling connotation.

By looking at the soundtrack of “Stranger Things,” it is clear that it is common for horror media to weaponize nostalgia from music to amplify fear.

Another popular media example is the recently released indie horror movie “Obsession.” In the final scene, the main character Nikki realizes her life is ruined because of actions she did against her will. As viewers hear Nikki’s gut-wrenching screaming, they can also hear the Little Dipper’s 1960 love song “Forever” playing.

The narrator of “Forever” is asking their lover to hold them and love them forever, because they are deeply in love. In comparison, all of Nikki’s problems are a result of becoming possessed by an obsessive version of herself.

When the lyrics of “Forever” are viewed through Nikki’s situation, the theme of everlasting love shifts to fit Nikki’s romantic fixation that was anything but love, which intensifies the haunting nature of the scene.

Traditional pop like “We’ll Meet Again,” “Mr. Sandman” and “Forever” have a distinctive sound compared to modern pop music. As a result, the contrast between the classic heartwarming songs and the creepy scenes works together to disturb viewers.

The right soundtrack can make on-screen horror jump from unsettling to downright horrifying, and that is the harmony of horror.