Between 1794 and 1939, there are nearly 300 works that use the Mozart theme--as adapted to fit the English lyrics "Away with melancholy, Nor doleful changes ring" (aka "O dolce concento").  Often it is used, like the Sor work, for variation sets.  These include variations for keyed ("Kent") bugle,  bassoon, flute, harp, piano four-hands, harp, carillon, etc. While visiting London in 1811, Felice Radicati (1775-1820) turned the melody into "Canone a Tre Voce" with chorus, orchestra and harp (manuscript in I-Baf: fondo antico FA1.3341). Flutist Louis Drouet toured with his Variations brillantes et favorites . . . sur l'air de Mozart O dolce concento exécutées dans plusiers concerts à S. Petersbourg, Vienne, Munich, Milan, Berlin, Florence (Milan: Ricordi, ca. 1825).   

The virtuoso insertion aria attributed to Angelica Catalani [see my Example 2] comes down to us in some dozen editions published in Paris, Edinburgh, London, Philadelphia, Boston, Vienna and Amsterdam; as late as 1871 a fresh orchestration was made by Friedrich Kücken and published by B. Senff in Leipzig.  The original variations were composed by Ferndnando Paër (and then elaborated upon by Catalani), since the earliest print (Paris: Naderman, 1817) attributes the "variations chantées par Madame Catalani au Théâtre royal italien" to him, and his manuscript  "messa in terzetto dal Maestro Ferd. Paer" (STB + orchestra) survives in the Openbare Bibaliotheek in Amsterdam (Kluis MS PAE-33).

An early arrangement for voice and guitar appears in the Entire New and Complete Instructions for the Guitar by a Professor (London: George Astor, ca. 1799).  Others include banjo (see Example 5), guitar (Converse, see Example 7 and Francesco Molino [as a "rondo" and in a variation set]), harmonium (Example 8). Et cetera, etc., etc.  The theme was quite famous when Sor encountered it and he may simply have wished to take advantage of its popularity. 

The theme also turns up as a temperance hymn (e.g. "Away with Melancholy, Let our Voices Sing" by John Pierpont [1985-1866]), as a fraternity glee for Bowdoin College (1839), and even as a Scottish fiddle tune, as well as a "Masonick"<!!!!> song.  The latter is of interest because of the Masonic overtones in Magic Flute. The Harvard Class of 1879 turned it into a clog dance, in Latin: "Musa sculponeis claudicat" ("Again January veils wintry skies in gloom."). It is also mentioned in novels by Chas. Dickens and Jane Austin.  Certainly the song with English and Italian words was very well known in the 19th century, but has simply dropped from sight in our day.  

Matanya Ophee has claimed that Sor used a special version of the tune made by Angelica Catalani with the assistance of Pergolesi, and the resulting melody is only vaguely like Mozart's.[i]  This is false. One wonders if he even consulted the music. 

See Example 1 (O cara armonia in the 1811 London score of Flauto Magico) and Catalani's variations in my Example 2.  BOTH ARE THE SAME MUSIC. AND THAT MUSIC IS MOZART'S. That theme and Sor's theme is the music that the slaves sing to the lyrics "Das klinget so herrlich."  A few repeated notes are added in adapting it to the English words, "Away with Melancholy" (compare Example 3 with Sor's theme in Example 0).  Notice also how someone has pencilled in the appoggiaturas in the score for "O cara armonia."  Many of the arrangements (including Sor's) are for amateurs, and so the ornaments (which professionals would add as matter of course) are written in "pour les dames," as the sheet music sometimes indicates.  These editions can be of special importance to performers today because they show how ornaments were improvised.  

The chromatic alterations (like the ugly ones that deface Mozart's melody in the Molino setting) appear in the SECOND, revised and augmented edition of Op. 9 publ. in Paris ca. 1829. The edition that identifies the theme on the titlepage as being "O Cara Armonia."  That is, the Italian text used in London, instead of "O dolce concento." (Example 1) for "Das klinget."  The libretto is by Giovanni de Gamerra, court poet in Vienna and librettist for Mozart's teenage opera Lucio Silla.  He made the Italian libretto used in London in 1811 for a Prague 1798 performance of Magic Flute.

In 1794, "Away with Melancholy" was first published in London by Longman & Broderip (probably the leading music publisher in Britain at that time), three years after the premier of Magic Flute in Vienna.  I've found other editions of the song in Dublin in ca. 1795 (which may have been issued before the London edition), and in Philadelphia in 1798 (see my Example 3).   One of the most popular version were the virtuoso variations for piano four hands  by Tatton Latour, court pianist to George IV, and partner with Cramer in the Samuel Chappell music publishing firm. His set of variations date from around 1800, and was reprinted in (by my count) some 33 editions, issued in London, Paris, Philadelphia, Baltimore, New York, Norfolk (Va.), St. Louis, Boston, Cincinnatti, Bonn, The Hague, Rotterdam, Amsterdam, and Sydney (see Example 9).  "Away with Melancholy" was apparently widely popular, and Sor could hardly have avoided it.  He probably wanted to cash in on its popularity with his guitar variations. 

[i] On August 30, 2007, Matanya Ophee wrote:

>>> The weight of the evidence is that it is from Mozart, via the kind
>>> elaborations of Paisiello, Catalani, Molino, Paulian and a host of
>>> other arrangers and re workers of the Mozart theme. If you believe
>>> otherwise, try and find it in the original score. As used by Sor, and
>>> a few others before him, that tune is not there. Period.
>
> There can never be a proof in such matters. We know for a fact that
> the Mozart aria, and the tune used by Sor are not the same. That's a
> fact. All you need to do is compare. (page 69, bottom system  in the
> Schirmer vocal score of The magic Flute). What we cannot prove is
> whether Sor took the elaborated theme directly from Catalani, or
> whether Catalani took it directly from Mozart and worked on it in her
> own special way, or that initial contrafact was made by Paisiello or
> Fioravanti who gave it to Catalani, or indirectly from Catalani via
> Molino, or from any other source with which we are not familiar today.

 

Not quite! Madame Catalani almost always sang a virtuoso insert aria when she appeared on stage.  It was in operas by Paisiello and by Fioravanti, among many others, that she sang the variations on "O dolce Concento."  The Paisiello opera was written in 1774, and it seems quite a trick for Paisiello to have made a contrafactum of a tune that wasn't composed until nearly 20 years later! Furthermore, the original variations are by Fernando Paer, not Catalani whose ornamented version is cited.