Mozart composed the String Duo K. 423 during a visit to Salz- burg from July to October 1783. According to his they were written to do his friend Michael Haydn a good turn. Haydn had been ordered to supply six duos for violin and viola to the Archbishop of Salzburg, but was only able to complete four of them due to a serious illness.
Mozart composed the two remaining pieces, and the „collection“ was presented to the Archbishop under Haydn’s name. To the present day, researchers have been unable to discover a contemporary print containing all six of the duos. One reason for this may be that Mozart’s duos clearly stand apart from Haydn’s, especially in the equality of the two parts and the ingenious handling of their themes.
The autograph manuscript of the duo has survived and is located today in the Robert Owen Lehman Collection of the Pierpont Morgan Library, New York. It was not used as an engraver’s copy for the first edition, which was issued by Artaria in Vienna only in 1792, and thus after Mozart’s death.
Here now is a performance of this wonderful work:
