The posthorn gets a solo in the Trio of the Minuet.[2]
Notes
^H. C. Robbins Landon, The Symphonies of Joseph Haydn. London: Universal Edition & Rockliff (1955): 116, footnote 13. "Serenade No. 9 in D major, K. 320; a symphony in A major by Michael Haydn (autograph: monastery of Göttweig) also uses a 'Corno da Postiglione' in the trio of the minuet."
A. Delarte, "A Quick Overview of the Instrumental Music of Michael Haydn" Bob's Poetry Magazine November 2006: 21 PDF
Charles H. Sherman and T. Donley Thomas, Johann Michael Haydn (1737–1806), a chronological thematic catalogue of his works. Stuyvesant, New York: Pendragon Press (1993)
C. Sherman, "Johann Michael Haydn" in The Symphony: Salzburg, Part 2 London: Garland Publishing (1982): lxviii