Haydn's last piano work is also considered to be his most famous single work for this instrument. The minor theme is filled with emotional depth: ''a melancholy andante in f minor, with variations, as only a genius can do them, that almost sounds like a free fantasia'' (thus described in a review of the time). The form is also demanding: not merely one theme but two - one in a major key, the other in a minor one - are varied in turn. The autograph gives one to believe that the work was originally intended to be the first movement of a sonata. This single edition has been taken from the recently revised volume of ''Piano pieces'' (HN 224) and furnished with a detailed commentary. Henle also recently published a facsimile of Haydn's autograph of the Variations in f minor: HN 3218.?