"His landscapes of those years [mid-1860s] reveal that he had rejected his earlier commitment to transcribing nature in the manner of Courbet, and was responding instead to formalist imperatives, including flat, decorative surfaces, subtle tonal harmonies, and allusive, rather than literal, subjects. Taking a cue from a critic who had referred to his early portrait of his mistress, 'The White Girl' (1862; National Gallery of Art, Washington, D.C.), as a 'symphony in white,' Whistler began to envision and entitle his works with the abstract language of music, calling them symphonies, compositions, harmonies, nocturnes, arrangements, and so forth."