Sonata in B flat major K.333 (1783–84)

There is also a concerto element in the Sonata in B flat that Mozart is though to have written in Linz in 1783, when he on his way back to Vienna after a trying visit to Salzburg undertaken to introduce Constanze to his disapproving father and sister. An extraordinary work, it could be taken as a symbol – although Mozart surely did not intend it that way – of the composer’s determination to shake off the past and not only embrace the future in Vienna but also push it ahead at his own accelerated pace. The past is represented by the decorous opening of the first movement with a theme borrowed from a Sonata, also in B flat, published in London six years earlier by the composer’s old friend Johan Christian Bach. While Mozart’s treatment of the material is much more interesting and while he establishes his own harmonic identity, there is little in the exposition to challenge convention. Early in the development section, however, he plunges without warning into F minor – which, given the simultaneous pressure of semi-quaver activity and syncopations high in the right hand, is a dramatic intervention in this context.

If Mozart’s more progressive contemporaries could have done something similar, even the most adventurous of them wouldn’t have had the imgination to think of some of the things that happen in the slow movement, let alone the courage to put them in writing. Again the introduction of the melodic material is unchallengingly decorous. Then, after the exposition repeat, a stinging dissonance opens a development of distressingly unsettled harmonies and correspondingly painful emotional disorientation. It is soon resolved but the experience is not forgotten.

The concerto element comes towards the end of the Allegretto grazioso, a rondo engagingly abundant in melodic ideas and harmonic diversions. Even in a movement as spontaneous as this, however, it is surprising to find the pianist indulging in a cadenza of concerto proportions – which is an opportunity not only for bravura scales and arpeggios but also for a new, extravagantly colourful and rhythmically insistent thematic development.