The story of Beethoven's Diabelli Variations is well known. The composer and publisher Anton Diabelli wanted to promote his new firm, and chose to do so by inviting fifty composers of varying fame to write a variation on his own waltz theme. Beethoven was, of course, the dominant figure in Vienna at the end of the 1810s, and his variation was to be the highlight. Yet Beethoven went rather further than Diabelli intended, writing thirty-three variations in 1819 and 1823, going one better than Bach in the Goldbergs, and completing what is surely among the most convincing of such piano works. Although not his last piano work, the variations sum up much of Beethoven's late style, as well as displaying an infectious vivacity less associated with this style.

So much we know, but more obscure is what happened to Diabelli's grand project. Published in July 1824, the work did indeed bring together Vienna's most famous names, even if most of them now languish in history's compositional dustheap. Andreas Staier, in this Wigmore Hall recital and on a rapturously-received new disc, pairs the Beethoven Diabellis with some of the Diabelli Diabellis. Hearing them side by side shows especially how far was Beethoven ahead of his time. Taking things another step forward, Staier – originally a harpsichordist in the HIP (historically-informed performance) movement – plays everything on a copy of an 1824 fortepiano by the Viennese maker Conrad Graf. So, this is cutting-edge composition played on a cutting-edge instrument of the time. As ever with HIP instruments, the Graf has its advantages and disadvantages. On the upside, it has a gorgeously fruity mid-range, and use of the resonances of the sustaining pedal and the nuances of the left pedal makes the instrument open to changes in colour. On the other hand, the top end is tinny, the mechanism seems less precise, and the bottom octaves lack weight. This performance, very disappointingly, did not employ the bassoon and janissary pedals heard on Staier’s new recording, which give the celebratory variations 20, 22, and 23 added shock value.

Staier played throughout this concert with a rhythmic abandon and a fluidity of tempo which might have seemed mannered on a modern piano, but helped with the fortepiano. This, and some occasionally rather imprecise technique, certainly saved some of the more banal of the Diabelli Diabellis. The published variations were of varying quality, and took varying liberties with the theme. Carl Czerny was instantly recognisable, his inane twirlings in an étude-esque variation characteristic of the composer. Conrad Kreutzer seemed derivative of Czerny, and Staier made the efforts of Johann Peter Pixis and Mozart's youngest son comical for all the wrong reasons: the former for his pompous left-hand work, the latter because the piece dissolved in its own runs. Frédéric Kalkbrenner sounded close to Beethoven's less inspired moments. Four of the variations intrigued. Joseph Kerzowsky's was simple, floaty, and slow, whilst Johann Nepomuk Hummel's featured some chromatic harmonies far removed from Diabelli's original. In a class of their own were the eleven-year old Liszt, whose torrents of notes seemed almost a parody of anguished Romanticism, and Schubert, whose major-minor trickery and tormented, delicate world hinted at the late piano sonatas.

Beethoven’s last piano work, the Op. 126 Bagatelles, separated the Diabelli sets. The Graf fortepiano’s inaccuracies made this music sound much eerier than usual, Beethoven’s harmonic inventions and thematic instabilities laid bare. The third Bagatelle in particular was sweetly played, a mix of turbulence and delicacy in a song without words. The martial fourth was characterful, the fifth full of beautifully cultured phrasing. Staier made the most of the sixth’s eclecticism (or genius, whatever you want to call it), and generally played up the wackiness of late Beethoven.

The Beethoven Diabellis are an immensely individual work, leaving the pianist great freedom of expression, even down to the pacing of pauses between variations. Staier’s rendition was constantly playful, easygoing, full of the humour often lacking in Beethoven performances (except those of Alfred Brendel), and ready to play rests and dynamic contrasts for their entire dramatic effect. He was, unsurprisingly for a Baroque specialist, especially good in variations which looked backwards, particularly at the fugal work hinted at in variation 4 and followed through in the fughetta 24th and the complexities of the penultimate fugue. Otherwise, though one could often quibble with the tempi of individual variations – for slower interludes were often taken too quickly for this listener – and at times with the number of wrong notes, the variations did emerge as a coherent whole, which is no small achievement. There was a sense of journey here, a joy not only in Beethoven’s writing but in the timbral possibilities of the fortepiano itself. Whilst a bit more poise and grace (especially in the three late slow variations) would have been welcome, wit more than compensated in a fine performance.