Piano Concerto No. 6 in D major, Hess 15

Unfinished – performing version completed by Nicholas Cook

In late 1814 and early 1815, Beethoven spent a good 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 sketches for the first movement. He even started writing out a full score (MS Artaria 184 in the Staatsbibliothek zu Berlin), which runs almost uninterrupted from the beginning of the movement to the middle of the solo exposition although the scoring becomes patchy as the work proceeds and there are signs of indecision or dissatisfaction on the composer's part. For whatever reason, Beethoven abandoned the work, and this torso of a movement (known to Beethoven scholars as Hess 15) remains one of the most substantial of Beethoven's unrealized conceptions"

More: http://unheardbeethoven.org/search.php?Identifier=hess15