From The Piano Guys:
Hello/Lacrimosa (or “Chello,” as it has affectionately been called in the studio) is a musical experiment bridging 18th century spiritualism and 21st century secularism. Imagine Mozart and Adele in the same room in an intense co-write session, quill and pen in hand, respectively. Picturing this hypothetical hangout helped to spark the creative combination of the two.