17 December

When Franz Schubert died in Vienna in 1828, he left behind several manuscripts of symphonies: works unpublished, and in some cases unperformed during his short lifetime. Nobody seemed much interested in these, even ten years later, when Schubert's posthumous fame was on the rise. Both Felix Mendelssohn and Robert Schumann did what they could to help promote Schubert's symphonies, but it wasn't until today's date in 1865-37 years after Schubert's death-that his most famous Symphony received its premiere performance in his home town of Vienna.
This Symphony in B minor came to be called the "Unfinished," since its manuscript score contained only two completely finished movements. A normal Viennese Symphony of Schubert's time should contain four movements, and, in fact, a fairly complete piano sketch of the third movement exists, as does a full score of just the first nine measures of that same movement.
When Johann van Herbeck conducted the Vienna Philharmonic in the first performance in 1865, he played the two surviving movements and tacked on the last movement of Schubert's Third Symphony as a finale. More recently, some scholars have argued that this music, a portion of Schubert's "Rosamunde" incidental music, was in fact the missing final movement of his symphony.

Despite these attempts to finish the "Unfinished," most performers and audiences seem content to hear the score as Schubert left it-romantically cut short, just like the composer's tragically short life. 
from American Composers Forum