Adagio and Rondo K617 for glass harmonica, flute, oboe, viola, and cello 

At some mellow moment at the end of a meal in congenial company you may have played musical glasses, moistening a fingertip and stroking round the rim of your wineglass. Given the right touch, each glass produces a small musical tone varying in pitch according to the amount of wine left in it.  

Musical glasses inspired the American sage Benjamin Franklin to invent a controlled instrument he called the glassychord or armonica. Mozart first heard it as a boy of eight on a tour in London only a year or so after its invention, played by a Miss Davies. Ten years later, he and his father, in Vienna, heard the glass harmonica again, played by Dr Mesmer, on a “much better instrument than Miss Davies’s” and better performed. Mozart played on it himself; and it evidently did not lose its charm for him, for the last chamber work he wrote, in the year of his death, was this Adagio and Rondo in C for Harmonica, Flute, Oboe, Viola and Violoncello, composed for Marianne Kirchgässner, a blind virtuoso then in Vienna. Mozart himself performed it, probably playing the viola, in August 1791. Despite keyboard and other refinements, the harmonica was an awkward instrument and appeared rarely after 1820.

The Adagio begins with a solemn, dramatic chord answered at once by the gravely gentle harmonica, setting off a phased dialogue exploiting the contrasting timbres of harmonica and ensemble instruments. Chord interjections and a small climax resolving into C major herald the Rondo. The harmonica introduces the cheerfully simple rondo theme. Brilliant alternations, both instrumental and thematic, cleverly combine with changes of mood that owe much to clever key modulations. Mozart’s good humour and wit prevail throughout.