Two sonatas later than Op. 90 (see above) Beethoven unleashed on the world his vast Hammerklavier Sonata, the term taken from the composer's insistence on the German rather than Italian (piano-forte) name for the instrument. It is a huge work, marking the extraordinary intellectual and physical demands Beethoven requires of his performers in the so-called Late Period (1817 onwards). During its 48-minute duration it balances traditional classical forms with amazingly imaginative and innovative gestures. The key, perhaps, to its four movements is its teetering on the very brink of unplayability — it tests technique as never before, yet that sense of struggle is integral to the work's success. The Canadian Anton Kuerti does a magnificent job with a work famed for its difficulty. As a contrast he also performs the "Moonlight" Sonata — beautifully!