Joseph Haydn's Horn Concerto No. 1 in D major, (Hob. VIId/3) was completed in 1762, "when Haydn was new to the Esterhazy court."
Because of the low range writing in the Adagio, some musicologists believe the concerto was written for Thaddaus Steinmüller. Other musicologists believe it was a present for the baptism ceremony of one of the children of Joseph Leutgeb (for whom Mozart wrote his horn concertos).
Horn Concerto No. 1 (Haydn) Wikipedia
The work is in three movements: