Answer
The answer is "Tout un monde lointain..", a cello concerto composed by Henri Dutilleux in 1970. Written in a single continuous movement, it showcases a range of emotions from its opening serenity to moments of intensity and contemplation. The concerto stands as a significant work in Dutilleux's oeuvre and the cello repertoire, characterized by its rich textures, lyrical melodies, and exploration of sound colors.