 Sadie observes that the K. 22 symphony composed in The Hague is a good deal more sophisticated than the earlier ones which were written in London.Mozart's creative progress is likewise reflected in the sonatas composed for the Princess of Orange, which, according to Sadie, mark a considerable advance in technique and ideas over the earlier Paris and London sets.The arias composed in the Netherlands include Mozart's first attempts at "aria d'affetto", "Per pièta, bell'idol mio", K. 73b, once thought to have been composed much later, as its higher K number indicates.