Marek Klein (1969) is intensively interested in Gregorian chant from 1992. Besides the self-study and liturgical praxis he attended several courses and events connected with Gregorian chant under the guidance of personalities such as Jiří Hodina, David Eben, Louis-Marie Vigne, Alberto Turco, Nino Albarosa, and Dom Yves-Marie Leliévre. He also participates in organising of events of this kind.He started his Graduale Project in december 2012 with the aim to record all of the chants included in the current Graduale — Graduale Romanum/Graduale Triplex. He writes about it: "When singing I use Graduale Triplex (1979) and I usually pay special attention to the St. Gallen neumatic notation. The performing of Gregorian Chant is different with every singer, and it is impossible to consider any way of performing as the only correct one. Neither do I consider my way of singing as the only correct one or the best one. I am also aware, that the chants of the Graduale (the main part of them) are not meant to be sung by soloist, but by a group of singers — a schola. I hope, however, that in spite of these drawbacks, my recordings will find their audience and that they can become a helpful resource for someone — a resource, which I was looking for without success at the time of my beginnings."