Heart Under was primarily recorded at Attica Studios in Donegal, with additional recording and post-production then completed at home. The album was produced by the band and mixed by David Wrench, whose previous collaborators include Frank Ocean, Let’s Eat Grandma, Jamie xx, FKA twigs and beyond. The title, Heart Under, comes from the lyric “the heart under its foot” from album track ‘Sore,’ and throughout recording the band discussed the idea of wanting the listener to feel like they’re on a train going through a tunnel. “This album felt very blue to us,” Ball explains. “There was sadness and sorrow in the album, and it felt like being underwater and under something very heavy. We let that influence the music, but it wasn’t a decision – it just naturally happened that way.”