I first met Thessa Torsing, the Dutch artist known as upsammy, on the platform at Amsterdam Centraal station in June. Her agent, Sören Schmidt, introduced us and we embraced awkwardly—she went for the handshake, I went for the hug. When the double-decker train arrived, the three of us, plus a childhood friend of Schmidt's, hopped on and found some seats. The small talk was flowing until a white-haired elderly woman came over and pointed to a sign that, I assume, read "Quiet Carriage" in Dutch. Our group exchanged glances, got up and clambered back downstairs.

We were headed to the small city of Nijmegen for Drift Festival, where Torsing was DJing on the main stage. De Vasim, a former factory located just past the elegant De Oversteek bridge, was both leafy and industrial, with shipping containers stacked opposite grassy ridges. By the time Torsing got the ball rolling with a slice of gloopy ambience, the sun was beating down, and the wide concrete dance floor was empty.

The unrelenting heat meant numbers barely improved over the next two hours, but the music was fantastic. Gliding from 90 through 124 BPM, Torsing touched on ambient, downtempo, instrumental hip-hop, dubstep, house, techno, IDM and whatever you'd call Amon Tobin's "Proper Hoodidge." Rhythmically and melodically the set was constantly morphing, with fresh drum patterns and tingling synth lines unfurling every few minutes. Her mixing was confident and sharp, full of tight blends that never hung around for too long. When she finished, closing with Neinzer's "Horus" off the recent Timedance compilation, she exited the booth and walked down to the dance floor, where a 46-year-old woman, a friend of Torsing's mum who had recently discovered clubbing, was bobbing animatedly down front.

This performance took place almost exactly a year on from Torsing's first proper gig, at the Berlin club ://about blank in June 2017. Since then, thanks to two killer EPs, a residency at Amsterdam's De School and a handful of excellent online mixes, she has shot onto the scene, presenting a broad and hard-to-define sound that champions weirdness over functionality. "I really hate it when people say, 'Oh upsammy plays electro.'" We were back in Amsterdam, sat outside in De School's pretty courtyard. Birdsong mingled with the chatter of friends enjoying barbecue and cocktails. A single turntable sat on a stone ledge, overseen by a young man with a crate of records and a plastic chair.

"Sometimes I go in that direction but I really don't like labelling my music," she said. "Maybe in a broader sense it can be a bit psychedelic, but I don't want to bind it to a genre. I think you can hear an upsammy record when it's a bit trippy or... I don't want to use the word 'sci-fi' any more, but a little bit quirky, a bit strange."

In person, Torsing was shy yet funny and quietly assertive. She was clearly getting used to talking about herself, but when it came to discussing her young career she showed conviction and ambition. When I said her style felt suited to warm-up sets, she agreed, before adding, "I've seen that now and I'd like to move on." She described making club music as "too limiting," while DJing, which has helped propel her into the spotlight, isn't something she sees a future in. "The ideal thing would be to have a live set," she said.

This restless attitude belongs to an artist uninterested in taking the easy route. When I asked Torsing if she had any go-to tracks for getting out of a tight spot, she seemed annoyed at the very concept, referring to them, in a sarcastic voice, as "trick records." In February, when she warmed up for Palms Trax in De School's basement, she was adamant that she wouldn't change her sound to please his fans. "My feeling was that if I give in now, if I just play smooth house, then I can never go back." Many up-and-coming artists in her position may have bent to the occasion, but Torsing says this is all part of the challenge. "The crowd isn't always going to go along with it, and I like that."

"Sometimes I'm afraid I expect too much from a dance floor," she continued. "It really depends on the venue, of course. But when I go out dancing I just want to be surprised all the time. I don't want to have to rely on taking a substance to have fun. I just want to hear the weirdness in the music."

One of Torsing's biggest stresses as a DJ is finding enough tracks that hit the sweet spot between weird and danceable. "Right now I'm doing it by mixing really danceable records with very spacey records," she said. "But then you sometimes get a set that's too dynamic. I notice that people just want a continuous groove."

I suggested that her own records fall into that sweet spot. Tracks like "Another Place" and "09-06," released as part of the striking Another Place EP in February, have eerie sounds and fizzing melodies set to slamming breakbeats. But Torsing said she wasn't "super fond" of playing her own tracks in DJ sets. "I would rather just do a live set that's totally me," she said. "Because it feels like instead of playing another great record by someone else, I'm going to play one of my own. It feels like I'm comparing. Maybe I'm not that proud of what I'm making, I guess."

Torsing currently lives in Amsterdam, not far from De School. After spending the first seven years of her life in Amsterdam, her family moved to Naarden, a small city in the north that's known as "the rich people area," she said. She attended a "really posh" secondary school, where she made a rebellious friend called Tristan, who, one King's Day, introduced her to her first rave at a small storage warehouse in Sloterdijk, on the outskirts of Amsterdam.

"I was going home and another friend was like, 'You need to come, you need to come.' They just dragged me there. I was 15 or 16 and it was the best time ever. I was just saying to my friend, 'Thank you so much for bringing me here.'"

Dance music was already a part of Torsing's life at this point—she loved CDs like Tiësto's Forbidden Paradise and MTV Lounge Vol.3 from her dad's collection—but the experience sparked a newfound love of partying. She, Tristan and two other friends formed a crew, putting on illegal raves in nearby towns and cities like Bussum and Hilversum. Their biggest event was in 2014 in a field near Amsterdam Science Park.

"We didn't expect it but all of a sudden there were like 400 people. We were selling laughing gas and made so much money, but it was also stressful because you didn't know who was coming and there were a lot of sketchy people trying to steal our stuff. I was always the concerned one. 'Where's this? Where's that?' All my other friends were just high and stoned. 'Thess, chill, nothing is gonna happen.' Then one time, when I wasn't around, Tristan took a balloon, fell on the bar and all the money fell out. Someone took it. €400 gone."

As well as making sure the events ran smoothly, Torsing would decorate the venues and DJ, playing everything from trance to techno. Gradually, spurred on by the loose atmosphere and non-judgemental crowds, she grew in confidence. "No one cared," she said. "Come on, it's a rave. I could just try any style, any genre."

When Torsing was 18, she moved to Utrecht to study Image and Media Technology at University Of The Arts Utrecht. By this point, she had started producing dance music—"really crappy deep house" inspired by what she heard at parties.

"I made music before but it was really weird, just reverb guitar with keys and weird sounds," she said. "It was super nice finding the four-to-the-floor beat. It gave me a grid to work from. My music was always super disorganised, just taking guitar riffs and looping. My dad used to be like, 'Just learn a song!' I was like, 'No I really like this line, I just want to repeat it!'"

Around this time she adopted the name upsammy, originally just for her visual art projects. It's taken from the song "Sammy" by Ramses Shaffy, a Dutch crooner who became popular in the '60s. In it, he sings "Hoog Sammy, kijk omhoog, Sammy," which translates as "High Sammy, look up high, Sammy."

During the winter of 2016, Torsing shut herself away in her bedroom and obsessively made tracks on Ableton, using the music as a way of escaping an unfulfilling internship. She began working the more psychedelic sounds of her youth—she used to be a massive Jimi Hendrix fan—into her productions. "I totally got sucked in and never got out of it. I was very emotionally connected to that music, really involved in it."

She uploaded a track called "Zona" onto SoundCloud and it was picked up by a local music head called Luke Cohlen, who invited her onto his radio show on the Utrecht station Stranded FM. There, she met Bob Verhoeven, another local head. He passed "Zona" to Sjoerd Oberman, founder of Nous'klaer Audio, a house and techno label from Rotterdam. Soon after, Oberman hit her up, asking for more tracks. "I was like, 'Yes, it's happened!'" she said. "I think I cried a little."

In September 2017, Nous'klaer released Paerels, a 12-track compilation of breezy ambient and techno. Torsing was the only artist to have more than one track featured. The beatless "Wish I Could Still…" opened the record, all wistful synths and exquisite melodies. "A Picture Of U" was more club-ready, with lopsided kicks stumbling beneath a lilting melody. Both cuts stood out for their 3D sound design and striking emotionality.

"Her tracks have a sort of simplicity, but they're also really deep in a genuine way," Oberman told me over Skype. "And she uses a lot of melodies without being cheesy. I was just super surprised she'd never released anything before."

Next, in February 2018, came Torsing's first solo EP, Another Place, also on Nous'klaer. This was my introduction to her music. The explosive title cut, in particular, blew me away. When I pressed Torsing on her favourite track, she went for the dank beauty of "Zona," which opens the EP. "I like it because it's so simple and it still has my guitar," she said. "I had put new strings on my guitar and you have these extra bits poking out the end, which you're meant to snip off. They were rattling, and that's the sound you hear in the beginning."

Torsing thinks her most recent EP, Words R Inert on Die Orakel, is currently the truest reflection of her sound. "On Another Place, I used a lot of Legowelt samples he put up on his site. The Hague-sounding stuff. But for my second release, I shaped the sounds more to my own: more filters, more sharpness. A bit more futuristic. Also the sound quality is a lot better."

Influential DJs—Avalon Emerson, Peach, Objekt—have supported Torsing's music, but it's her residency at De School that has arguably played the biggest part in her rise. Luc Mastenbroek, the club's booker, first discovered her in early 2017 via a Stranded FM mix, which he described to me over email as "really nice daytime typing music." He booked her to play an ambient set in the garden on a sunny Sunday afternoon in July, followed a month later by a set in the airy second room upstairs, warming up for Jane Fitz. During one of the club's marathon ADE weekenders, she played in there again, this time taking the tricky Sunday morning-into-afternoon slot.

"It's a super hard slot actually," Mastenbroek said. "You play for a combination of fresh people who still have to warm up and ravers who've been there for a while. When the weather is good, most people go and chill in the garden, so it's hard to keep people inside. The only way to keep everyone in is to play with a constant groove, but always interesting and cheerful, a certain softness to it. A big-room Italo record will probably make people leave, same as hard techno or distorted wave edits. But there's this in-between-sound, somewhere between Hessle Audio, DJ Sprinkles and B12, that became sort of the trademark for that moment and her sets there."

"Most young DJs, the first time they play De School they tend to overdo it a little—they play all their favourite tracks, please all their friends in the front, do all their trademark transitions they've practiced 100 times at home," he continued. "She's the first DJ I've met who didn't play this way—she just kind of walked in and played this perfect Sunday morning music to dance to. It's the hardest spot to play, but when you pull it off it's the most magical."

The day after Drift Festival, I saw Torsing play that exact slot at De School. It was another sprawling Het Weekend session, run in collaboration with the German festival Nachtdigital. When I got there around midday, most of the crowd had decamped to the garden. Dozens of weary ravers lay sprawled across the gravel, some doubled over onto their partner's laps. Tucked away in a corner, cheery vendors served pancakes and toasties to those who could stomach it.

Inside, dappled light from the backdrop of green trees framed Torsing's silhouette. The room was about one-third full—the dregs from Saturday night. She was playing tough and upbeat, moving from half-time drum & bass to chugging breaks with tart acid lines. The bleeps of Steffi's "Kokkie," a track I'd recognised from her set the day before, had me running over to ask for the ID.

For the final hour, Torsing lent into Mastenbroek's "in-between-sound," a kind of bassy electro with soft edges. That morphed into tracks with a light-footed '80s feel. With 30 minutes to go, the room swelled with fresh faces—the party shedding its skin and forming a new one. Even so, Torsing barely looked up from the decks, too absorbed in the next transition. She closed with a glistening electro track by Ariadne's Labyrinth called "Patternicity." As she stepped away from the decks, Schmidt, her agent, gave her a playful shove of congratulations.

Three weeks later, Torsing graduated from university and overnight became a full-time DJ. Up until that point, she'd been holding back from gigs to concentrate on her final piece, a sculpture of rock and sand that she described as a "monument for eternal destruction." Soon she'll be on the road, playing two shows a weekend minimum. On August 25th, she'll make her debut at Panorama Bar. I wondered if the prospect of touring was worrying her.

"I'm super excited but also curious how I'm going to handle the travelling," she said. "I'm not very nice when I'm tired and I don't play well if I'm grumpy. But on the other hand, the more I play, the more I have a mode that I just turn on. You get into a zone and you focus right away. Also when you tour, I can imagine that you meet a lot of people and it's all very short-term contact. It's all about small talk and that's not really my strong side. Some people might say I'm an introvert, and the scene feels very extroverted."

After summer, she hopes to return to 33/45 Vinyl Records, the store in Leiden where she worked one day a week until recently. The rest of her time will be spent making music. Another EP for Nous'klaer is on the way in October, and she's also signed a split 12-inch to the Whities Blue series with the Stoke-born artist BFTT. I've heard both of her tracks on that one, and they're as good as anything she's released.

Further down the line, Torsing has film scores and an ambient album in her sights. She got a taste for the former at this year's Dekmantel Festival, where she composed a new soundtrack for Uit het rijk der kristallen, a short by the Dutch science filmmaker Jan Cornelis Mol, made in 1927.

"I just hope I don't get an overdose from music, you know what I mean?" she said. "Music used to be an escape for me and now music will be the main thing. So I guess I will want to escape from it. But we'll see. I don't let myself get too excited about it because there's also a feeling that it could be over at any minute. You never know in these times how fast people come and go. It's just important to do what I do and not think too much about what's out there."