In the latter part of 2014, part of Mozart’s manuscript of the Sonata, K.331 was found in Budapest. The manuscript, with the exception of the last page of the last movement, 'Rondo alla turca', had so far been considered missing under mysterious circumstances.

The new Urtext, according to the pianist’s statement, not only contains alterations in the phrase markings, articulation, rhythm and dynamics, but there are some different notes as well. The opening of the second movement is particularly interesting for William Youn: “With the new phrase indication and new note (A instead of Csharp) in the third bar, I play the entire phrase with a completely different agogic quality, which lends it a different character as well. Bars 24–26 of the same movement have always been played in the minor key up until now – and they are now suddenly in major!”