We don’t know why it’s unfinished – he went on to write Symphony 9 (the ‘Great’ in C major). It’s possible he was interrupted by syphilis or working on another piece such as the Wanderer Fantasy. It was most likely composed as a thanks to the Graz Music Society who had given him an honorary diploma in 1823.
The melodic material could all easily come from Schubert’s Lieder. It starts in sonata form with a low B minor melody answered by a theme in the oboe and clarinet (the first subject). The second subject is more cheerful in G major, and more well-known.
The slow movement is an Andante con moto in E major, contrasting two themes. There exists a fragment of a Scherzo in B minor with a G major Trio.