The 55 Haydn Sonatas are perhaps the least-known treasures of the piano repertoire. In them one can hear Haydn virtually inventing the classical style, from the early, somewhat tentative beginnings, through the bold experiments of the 1770s, to the adventurous late works. As with Beethoven (Haydn’s somewhat recalcitrant student) each sonata is a new exploration, and the element of surprise is ever present. Haydn delights in abrupt transitions, twists and turns, sudden pauses, and apparent non sequiturs; listening to him demands a constant alertness.

The E-major Sonata’s first movement, with its quick changes, lively rhetoric, and sudden emphases – the jolting chord that begins the development – is a prime example of the middle-period sonatas. The Andante is a gently sad lyric piece, mostly in triplets. The last movement is a noble minuet with contrasting trios in the minor; each part is inventively varied – no composer loved variations more.

Many of Haydn’s string quartets bear curious nicknames (“The Lark,” “The Razor,” “The Frog,” etc.). I am tempted to call the very serious B-minor Sonata “The Bear”; the lumbering bass figure at the beginning, the repeated chorded growls in the bass, and a general air of surly brusqueness give it unusual power. In exquisite contrast, the central Minuet is one of the most delicate and graceful pieces Haydn ever wrote – an unusually Mozartean moment. The bear returns in the minor-key trio, accompanied later on by some angry bees buzzing in the right hand. The Presto hammers away in repeated notes, at the first movement’s opening third, and the bees also return with a vengeance. The end is stark and uncompromising.

In total contrast, the C-major Sonata of 1795 is an effervescent example of the late Haydn. (It might be mentioned here that Haydn wrote 37 piano trios, most of them rarely played and full of wonderful music.) The mischievous staccato opening idea receives the full treatment: contrapuntal development, rhetorical slights of hand, sudden lyric flights, and remarkable pedal effects in bass and treble. The calm serenity of the Adagio is enlivened by elaborate and wide-ranging ornamentation, which in Haydn is less vocal than instrumental in its figuration. The development lends a tinge of minor darkness. In the finale, a jaunty scherzo-like theme has great trouble getting anywhere, as it keeps being rudely interrupted by dissonant harmonies and sudden pauses, till finally it succeeds to general rejoicing – all this in under three minutes!