Pairing unusual rhythmic structures with pop melodies, British math rock quartet Delta Sleep grew out of a Canterbury act, Sávlön, before settling on their new moniker in Brighton. Their first two full-length releases -- 2015's Twin Galaxies and 2018's Ghost City -- were both concept albums that built up a cult following. This led to a 2019 world tour on which they recorded alternate versions of tracks from their repertoire, released the following year as Soft Sounds. A 2021 album, Spring Island, was preceded by the Old Soul EP.