Peter sought instruments that could blend chords and melodies for his project, The Sift, experimenting with various instruments like the harmonium and pipe organ without success. He discovered the harpejji, which combines elements of a piano and guitar, and it became essential in shaping The Sift’s sound. Peter also incorporated a guitar recording into the track 'Wellspring' by collaborating with musicians Pontus Fällman and Gabriel Holmertz, who introduced a lap steel guitar instead of the harpejji for the melody. This change contributed to the "soul sound" of the game, enhancing the overall gaming experience.