La Contessina (The Young Countess) is perhaps Gassmann's best-known opera. As is the case with Il filosofo innamorato the libretto of La Contessina was adapted from Goldoni by Coltellini. The work received its premiere in Mhrisch-Neustadt on 3 September 1770 during festivities to celebrate the meeting of Joseph II and Frederick The Great. The work was highly successful and was produced in a number of important European musical centres. As a measure of its popularity the overture was advertised for sale in the Breitkopf Catalogue (Supplement VIII 1773) and also found its way into the Quartbuch catalogue. The Viennese court copy of the score - upon which this edition of the overture is based - is bound in three volumes and titled 'La Contessina / Del Sig: Floriano Leopoldo Gasmann'.
In producing the score the copyist adhered to the usual time-saving conventions of the period: where the violins play in unison, the second part is not notated; similarly, the viola line is left blank unless it is playing independently of the basso part. As the copy was doubtless prepared under Gassmann's direct supervision it should be considered a highly reliable source. Nonetheless, there are inconsistencies, errors and the odd omissions. The style and notation of articulation and dynamic markings have been standardised throughout, and, where missing from the source, markings have been reconstructed from parallel passages. These are indicated by the use of dotted slurs or brackets. Like most eighteenth-century sources, the present manuscript is inconsistent in its notation of appoggiature; these too have been standardised to minimise confusion. Obvious wrong notes have been corrected without comment; editorial emendations with no authority from the source are placed within brackets.