Although the autograph bears the date 1771, Haydn withheld publication of the famous C minor Sonata, No 20, until 1780, when it appeared as the last, and by far the most challenging, of the set dedicated to the Auenbrugger sisters. With its abrupt dynamic contrasts, this is the first of Haydn’s keyboard works conceived essentially in terms of a touch-sensitive instrument—either the clavichord or the new fortepiano—rather than the harpsichord. Its expansive scale and virtuoso demands are unprecedented in Haydn’s sonatas before the 1790s, while its tragic intensity is matched in his keyboard music only by the F minor Variations of 1793. This is Haydn’s ‘Appassionata’. The first movement—whose elegiac main theme in parallel thirds and sixths Brahms perhaps subconsciously recalled in his song of a dying girl, Immer leiser wird mein Schlummer
—combines soulful Empfindsamkeit, Sturm und Drang turbulence and argumentative rigour. Haydn enhances the music’s poignancy with passages of ‘speaking’ recitative, like heartfelt oratory.
The Andante con moto, in A flat major, unfolding over an expressive running bass line, is another Haydn slow movement with a distinct Baroque flavour. But with its textural complexity and wide harmonic reach it inhabits a different world from the earlier sonatas. Constant syncopations give the music a restless, yearning edge, rising to passion in the mounting sequences that sweep the music into the recapitulation. The finale, written against the background of a fast minuet, has a latent despairing fury that becomes manifest towards the end. Mingling violence and virtuosity, Haydn here expands a brief toccata-like sequence in an astounding crossed-hands passage, with the left hand touching the extremes of the contemporary five-octave keyboard.
from notes by Richard Wigmore © 2012