Ólafur's fourth official solo album, re:member, was released in August 2018. The album featured his ground-breaking new musical system called Stratus. The Stratus Pianos are two self-playing, semi-generative player pianos which are triggered by a central piano played by Arnalds. The custom-built software was born out of two years of work by the composer and audio developer, Halldor Eldjarn. As Arnalds plays a note on the piano, two different notes are generated by Stratus, creating unexpected harmonies and surprising melodic sequences.
The algorithms generated from Stratus were also used to create the album artwork. In an interview with Sound of Boston Arnalds explains that the artist, Torsten Posselt from FELD studios, used the Stratus software as a starting point and made his own software that translated the same MIDI signals used for the music. Each dot corresponds to a piano note in the title track: 88 fields correspond to 88 notes; the thicker the dot, the higher the frequency of that note being played.