Lo Vas a Olvidar

On February 26, 2019, American songwriter Billie Eilish told BBC Radio 1 that she and Spanish singer Rosalía had a recording session where they made a song together.^[1] Eilish also talked about what it was like to work with Rosalía: "It was great, she actually knows what she wants," Eilish said. "That's why it was kind of refreshing 'cause I was like, 'Wow, you're the only other person I've really met that's like this'".^[2]

Eilish performed a concert at the Sant Jordi Club in Barcelona on March 9, and the following day Rosalía posted a picture of both on social media and stated "can't wait to finish our song. Sharing with you in the studio or seeing you live yesterday inspires me very much".^[3] Later that month Eilish revealed that the song was half in Spanish and half in English and described it as "beautiful",^[4] and said that they were "both in love with it".^[5] Due to Rosalía embarking on her El Mal Querer Tour from March to December 2019 and Eilish preparing for her When We All Fall Asleep Tour (which ran from April to November) the song remained unfinished due to scheduling conflicts.^[6]

In January 2021, producer Finneas O'Connell expressed admiration for a Billboard article about the bilingual collaborations the magazine anticipated.^[7] The official announcement of the song was made on January 19 on social media, alongside the trailer for "Fuck Anyone Who's Not a Sea Blob" the second of two specials of the American teen drama series Euphoria.^[8][9] The episode was broadcast on HBO on January 24,^[10] after being broadcast early on HBO Max on January 21.^[11] "Lo Vas a Olvidar" featured prominently in the bottle episode, which depicts Hunter Schafer's character Jules Vaughn in therapy, and plays over a scene of flashbacks to Euphoria protagonist Rue Bennett (Zendaya).^[12] The song was the third single to the compilation album, Euphoria Season 1 (An HBO Original Series Soundtrack), released on May 14.^[13]

"Lo Vas a Olvidar" is a hymn-based ballad incorporating "inventive art pop".^[14] Steffanee Wong of Nylon stated that the song is sung entirely a capella, and mentioned it had "sparse nature sounds and atmospheric synths forming a misty backdrop, as Eilish and Rosalía do vocal gymnastics around each other, sometimes in English but mostly in Spanish."^[15]

During an interview with Lowe, Eilish stated that the making of this song "is the longest lead-up in the world". The first joint recording session took place in Los Angeles in January 2019, where most of the song was written and recorded. During the session "Rosalía had opened a channel in Eilish that she hadn't tried before", reaching a new range of high notes. Eilish insisted on singing in Spanish, because the language "makes you sound better". Rosalía coached the non-fluent Eilish and translated the lyrics to her. In July, a second collaborative session was held in the United States.^[16]

In April 2020, Rosalía told Zane Lowe that while in COVID-19 lockdown, she had been working on the track for over two consecutive weeks.^[17] By that time the arrangements, the production design, and Rosalía's vocals were completed,^[18] only Eilish's vocals needed to be sent.^[19] Producer Finneas O'Connell told the press that the song went through a lot of stages, something quite rare since he and his sister usually keep the first impression as the final sound.^[20] Rosalía's part and the arrangements for the song were reportedly finished by April 2020. Although the track was scheduled to be released during summertime in 2020,^[21] the production was revamped during that time and the final verses were added by Eilish with a little help from other O'Connell family members.^[16]

A music video for "Lo Vas a Olvidar" was released the same day as the song.^[22] The video was directed by Nabil Elderkin.^[22][23][24] The music features Eilish and Rosalía alone in a dark room, lit only by a moving spotlight, singing into a shadowy and stormy void.^[25][26][27]