Symphony No. 20 in D major, K. 133, was composed by Wolfgang Amadeus Mozart in July, 1772, when Mozart was sixteen years old. This symphony is one of many written during the period Mozart stayed in Salzburg, between two trips to Italy. Compared to other symphonies Mozart wrote in this period, the scoring is extravagant, featuring two trumpets in addition to the standard oboes, horns, and strings. The key of D major, which is a key often reserved for ceremonial music, is well suited to the presence of these trumpets.
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