The main aim of this paper is to examine the stylistic and aesthetic differences between nineteenth- and twentieth-century ideas about orchestral arrangement. The examination is based on a comparative study of two orchestral arrangements of Mussorgsky's Tableaux d'une exposition: one by A. Touschmaloff (1861-96), a pupil of Rimsky-Korsakov, and the other by M. Ravel. Even though Touschmaloff might have claimed that he elaborated Mussorgsky's thoughts as faithfully as possible, his version of Tableaux is a distortion of the original composition, since the peculiar quality of roughness in Mussorgsky's piano music is virtually emasculated in the process of 'refining' by the arranger. This kind of 'faithfulness' to the original composition is what is specific to nineteenth-century arrangements in general. In contrast with Touschmaloff's orchestration, Ravel must have been aware that he was arranging the original work in his own way - and this is where the two versions differ most significantly from each other. Ravel never failed to understand and appreciate the essential character of Mussorgsky's piano writing. He created a new phase by making a conflict between the musical identities of Mussorgsky and his own. This kind of stylistic deformation is therefore completely different in concept from the traditional nineteenth-century approach to arrangements.