Peter Green, in The New Republic reviewing a volume of letters of Ernest Hemingway, says some things that seem equally applicable to Goethe, especially in regard to creating a literary persona. For instance, despite one or two intriguing items, Hemingway's early correspondence offers mostly "unconnected glimpses from a life: glimpses invariably given the particular slant that 'the enditer of this screed' (as young Hemingway frequently referred to himself) for one particular addressee (father, mother, siblings, friends at school or work, ex-buddies from the Italian front) at one particular time." From this, Professor Green goes on to assert that Hemingway was a "classic compartmentalizer when it came to human relationships," adapting his style to audience.
If one reads Goethe early letters, particularly those he wrote while he was a student in Leipzig, one sees something similar. The tone of his letters to his younger sister, for instance, are playful, while ladling out big doses of instruction. He switches languages, venturing into French and even English, in which he composes a poem. (Interestingly, Professor Green mentions that the letters of schoolboy Hemingway are "dotted with ungrammatical and syntactically illiterate Latin phrases"; the same is true of the Italian and French in his later letters.) That Goethe is trying out different styles and forming a literary personality is evident in the letters he writes to his friend Behrisch at the same time. These letters constitute a small play modeled on Lessing's Miss Sara Sampson. (Take my word for it; I have written an article on this subject. See Goethe Yearbook, vol. 8.)
Basically Goethe was imitating the style of other writers, and Hemingway also came by his craft in a similar way. Green mentions that Hemingway got a job in 1917 as a cub reporter for The Kansas City Star, covering City Hall, the courts, police blotter, etc. He learned thereby to "write with accuracy and brevity, stressing the facts, eschewing opinions -- training that proved invaluable later when he began hammering out his fictional style." So, nothing out of the ordinary here -- simply a practice of all the most notable writers.
The letters in the Hemingway volume span the years 1907 to 1922 and represent the first of a planned sixteen volumes. I'm not a scholar of Goethe's correspondence, but he may have written more letters. Unlike Hemingway, however, who penned (or typed) his own letters, Goethe began very early dictating his correspondence, along with his literary efforts. Rome may have been an exception, though he was accompanied there by a servant/factotum. (Certainly the diary he kept on his journey to Rome was heavily edited before publication as Italian Journey.) By the end of his life the tone of his letters is a monotone, perhaps a function of dictation. By then, of course, as the painting at the top of the post reveals (from 1831), he had created a persona that matched his self-image.
Picture credits: Recherche; Renegade Blog