Mozart composed the String Duo K. 423 during a visit to Salzburg from July to October 1783. According to historical notes, they were written to do his friend Michael Haydn a personal favor. 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.
Here is an amazing performance of Duo KV423 by David Oistrakh, viola, and his son, Igor, playing the violin part.
