Guillaume Lasceux (1740-1831) was a French organist.
His music - which it's fashionable to despise - is rooted in the French tradition, but also strongly influenced by the Viennese classicism.
This simphonie concertante seems, imho, a a joyful way to begin the year. Written to be played during the offertory, it shows a mix of Haydn and of merry-go-round or military music, all that using the usual "grands jeux" registration. The result is typical of the French post-classic organ school. Some hate (not I), some like and smile....
I discovered this piece in a recording by André Isoir, who plays a shortened version of the original. So, I followed ...IMHO, the missing bars add nothing to the piece and rather tend to make it a bit too long and repetitive.