Rosalía and Billie Eilish first teased a possible collaboration in the before-time of 2019, when the Spanish singer posted a washed-out Polaroid from a studio session that promptly sparked rabid discussion about which direction the shape-shifting pop stars might take. Two years later, the pair have finally followed up with “Lo Vas a Olvidar,” a hypnagogic and muted duet produced by FINNEAS. Filled out with little more than reverb-heavy synths and the duo’s plaintive harmonies, the ballad is a departure from both artists’ more energetic singles over the last year, with Eilish providing a compelling Spanish-language debut of her own. The subdued, deliberate pace of “Lo Vas a Olvidar” bolsters the melancholy lyrics: “El amor no puede medirse en un paso firme” (“Love cannot be measured steadily”), Rosalía sings in a gently tumbling vocal run about a love gone sour. “Un día soy un dios y al otro puedo partirme” (“One day I’m a god and the next I can break”).

If the mood seems overwrought, homing in on the ephemeral nature of even the most passionate romance, that’s kind of the point: “Lo Vas a Olvidar” accompanies a special episode of HBO’s high school drama Euphoria premiering this weekend, and its tormented lyrics, hushed ambience, and Auto-Tuned vocals feel calibrated for the show’s high-pitched, Gen-Z melodrama. Nonetheless, Eilish and Rosalía’s rich harmonies create a supernal vibe entirely their own, amounting to a decent if inessential addition to their catalogs.