The reason that there are six versions of the song "Die Forelle" ("The Trout") is that friends asked for copies of this particular favorite, and Schubert willingly wrote out new copies, with the minor variants that memory introduced. Schubert started making music among his friends at choir school in Vienna; he planned operas with his friends, who sometimes wrote libretti for him; he played for "Schubertiades," concerts of his music, in friends' houses; and he wrote songs for his friends, often settings of their own poems.
Schubert's lifestyle was ultimately his own undoing, ruined by sexual adventuring and the syphilis that resulted. The tragedy of this serves as a guidepost to any understanding of the last five years of Schubert's life. The works of that period -- "Winterreise," the Heine settings, the string quintet and the piano sonatas (from A minor of 1825 to the visionary triptych of the last years) -- are central to our sense of a transition from monumental classicism to early Romanticism. They prefigure much of late Romanticism and of modernism too.
On his deathbed the composer alternated between reading James Fenimore Cooper's "The Last of the Mohicans" and correcting the proofs of "Winterreise."
Source: The Wall Street Journal Book Shelf May 13, 1997 pg. A21