The second Horn Concerto KV.417 indeed was written in 1783, 27 May to be precise. However, with the Third Concerto KV.447 we are less certain: the Romanza is thought to be composed in 1794, but the outer movements supposedly originated in 1786-1787. The Forth Horn Concerto KV.495 finally can be dated accordingly to Mozart's VerzeichulB aller meiner Werke: he wrote it in 1786 'fur den Leitgeb'.

Joseph Iganz Leitgeb (or Leutgeb) like Mozart had been serving in Salzburg. Born circa 1745, he was appointed Jagerhornists in the Archbishops orchestra in 1770. Seven years later, after travelling to Paris, Vienna and Milan, he moved to Vienna where he died in 1811. Mozart and he were close friends in Salzburg and in Vienna. Mozart mentions the horn player in the last letter to his wife, two months before his death: 'Leitgeb and Hofer are just here. The former is staying with me for dinner'. It is claimed that Mozart wrote all his horn concertos for Leitgeb, including those two that had been lost.

The instrument for which Mozart composed is different from the current. Valves were added later and the player only had his lip preasure to produce a harmonic series on a certain fundamental. Four of these harmonics were out of tune but could be played when moving the hand deeper into the bell and thus bringing forth stopped notes. Leitgeb's horn must have had E flat as the fundamental, since three of the concertos are in that key. By means of a crook however, it was possible to increase the basic length producing for instance D as the fundamental.

For players of the modern horn, Mozart's concertos are still very demanding but what it must have been like in the eighteenth century, is humorously demonstrated by the italian remarks Mozart added in the Concerto KV.412: 'Come on - quick - get on - be a good fellow - courage'. And near then final shake, 'little donkey' Leitgeb is admonished: 'A sheep trill - ready? Thank heaven - enough, enough!'