Once Twice Melody received universal acclaim by music critics upon release, and debuted at number 12 on the US Billboard 200 chart, with 24,000 album-equivalent units.

[1] It was then announced in February 2021 that they would contribute to arts company Meow Wolf's interactive exhibition Omega Mart, releasing a short film titled "Marin's Dreams" on April 22, 2021.

[24] Reviewing the album for AllMusic, Heather Phares claimed that, "Though Once Twice Melody is unapologetically lush even by Beach House's standards, the duo uses space creatively to express the beauty in sadness.

"[26] Stevie Chick of Mojo called it the band's "grandest vision yet", praising the "impassive beauty" of Legrand's vocals and comparing them to "'O Superman'-era Laurie Anderson serenades, or as if someone programmed AI to sing like Judee Sill.

"[6] Jason Anderson of Uncut commended the "stunning" cinematic quality of the first chapter and praised the album's "unexpected elements" for deftly counterbalancing the "grandeur and glamour from becoming sickly sweet."

Uncut concluded that the album's "greatness lies not in its hugeness – it's in the duo's ability to create music that possesses the same intimacy regardless of its scope.