Beethoven Piano Concerto no. 6. Piano Concerto No. 6 in D major, Hess 15 is an unfinished piano concerto by German composer Ludwig van Beethoven. In (estimated) late 1814 and early 1815,[1] Beethoven spent a great deal of time on a project that never reached completion: a piano concerto in D major, which would if completed have been the sixth. He made about seventy pages of sk..