The Missa Solemnis in D Major, Op. 123 was composed by Ludwig van Beethoven from 1819-1823. It was first performed on April 7, 1824 in St. Petersburg, under the auspices of Beethoven's patron Prince Nikolai Galitzin; an incomplete performance was given in Vienna on 7 May1824, when the Kyrie, Credo, and Agnus Dei were conducted by the composer. It is generally considered to be one of the composer's supreme achievements. Together with Bach's Mass in B Minor, it is the most significant mass setting of the common practice period.
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