First is a piece of chamber music: the Piano Quartet No.3 in C Major (WoO 36, no. 3). A piano quartet is basically a string quartet with the second violin removed and a piano substituted. Piano quartets are generally uncommon, and the three Quartets in the WoO 36 group are the only ones he composed. In fact, they were never published until after his death, and Beethoven wrote the three Piano Quartets when he was only 15. They show a heavy influence of Mozart, and according to my reading, they even use some of Mozart's thematic material, although I couldn't tell you where. The work is charming and, well, pleasant in the most wonderfully Classical way. And he wrote this when he was fifteen. Yikes!
And if Beethoven at 15 was impressive, let's turn back the clock to when he was just 12. This is, by all accounts, the first published piece Beethoven ever wrote, when he had undertaken lessons with Christian Neefe, one of the most prominent musicians in his hometown of Bonn, Germany. As an exercise, Neefe had assigned his young student to write a series of variations on a march by a composer named Ernst Dressler, and this seven-minute work is the result. It's not particularly profound, but one can definitely tell that this was a twelve-year-old with a keen ear and a strong sense for thematic possibilities.
More Beethoven to come! We're only just getting started.