On Nov. 4,pin up doll sex playing video game 2021, creator Andy Koh posted a TikTok captioned, "day 1 of listening to 2020 tik tok sounds to feel something."

He had recently moved to South Korea and was looking for ways to entertain himself while completing his mandatory two-week quarantine. So he turned to TikTok, specifically the nostalgic sounds of early pandemic life. The first sound he reacted to was BENEE's "Supalonely (Feat. Gus Dapperton)," which sparked a popular dance trend on the app during the dawn of the pandemic. Three weeks later, Koh's video has garnered over 6.7 million views and 1.5 million likes.

Koh quickly realized this was a bittersweet feeling most TikTok users could relate to. So far, he's posted 14 videos in the series. 

And he's not the only creator who has been revisiting the early days of the pandemic. In September, The Atlanticreported on the subculture of creators on TikTok and YouTube who feel nostalgic for peak pandemic content. "These 'early-pandemic aesthetic' creators have built an online community tied together by a yearning for a time when the world seemed united in facing an uncertain future," writes Morgan Ome.

You may think that these TikTok earworms from 2020 — you know, the ones that overran your For You Page for months on end — wouldn't hold up now, but they're actually eliciting rich emotional responses from users like Koh. 

"What is most interesting is how there seems to be almost a collective consciousness triggered by these sounds," Koh tells Mashable over email.

And there's a neurological reason for that. According to Sandra Garrido, a music and mental health researcher at Western Sydney University, music and sounds are some of the biggest triggers of nostalgia.

"One of the big mechanisms by which we have an emotional response to music is memory," Garrido explains to Mashable, citing a 2008 research study from Patrik N. Juslin and Daniel Västfjäll titled "Emotional responses to music: The need to consider underlying mechanisms." In it, she says, "They argue that hearing just a snippet of music can take us right back to a place we were before or can remind us of a place or a time where we were before."

These TikTok sounds do just that.

If you were on TikTok in early 2020, then chances are Koh's series will make you, well, feel something. Songs like Curtis Roach and Tyga's "Bored in the House," Chip Tha Ripper's "Interior Crocodile Alligator," and Tiagz's "Heart Went Oops" will most likely transport you to a surreal period of time synonymous with uncertainty, whipped coffee, the word "unprecedented," and the first season of Tiger King.

Just take a look at the comments on Koh's TikToks. One user writes, "can’t tell if i’m feeling nostalgia or ptsd," and another comments, "chloe ting, tiger king, whipped coffe, baking bread." But the resounding sentiment that Koh seems to be capturing? As one commenter puts it, "pls why does this make me wanna cry." 

This is a completely normal response, says Garrido. Research suggests that nostalgia is a way for us to reflect on our personal narratives. "It can be affirming to look back on the things that happened during our lives and how they’ve shaped who we are now," she says. "We all need to feel connected to our past."

It’s been nearly two years since the beginning of the pandemic and "there’s a lot of processing to be done,” adds Garrido.

So it makes sense that these viral TikTok sounds are a way for us to contextualize such a confusing and traumatic time.

It's what inspired Koh to take on the challenge in the first place. "I had taken a hiatus from TikTok before coming to Korea, but as soon as I revisited some of the older videos and sounds I had favorited, I felt a strange combination of nostalgia, sadness, and joy," he says.

“I think that we, as a society, will be peeling back the layers of last year for quite some time," Koh adds. "Speaking for myself, I’m still processing March 2020. I think that as long as we have strong memories and sentiments from last year, these sounds will always contain an incredible amount of emotion."

We may no longer be bored in the house, but we'll never forget how it felt — or sounded.