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 May 1824, 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.
Unquestionably a great work, representing Beethoven at the height of his powers, it has notably failed to reach the popularity of many of the symphonies and sonatas. Written around the same time as his ninth symphony, it is Beethoven's second setting of the mass, after his Mass in C, Op. 86, a work far less admired.
The mass is scored for 2 flutes; 2 oboes, 2 clarinets (in A, C, and B♭); 2 bassoons; contrabassoon; 4 horns (in D, E♭, B♭ basso, E, and G); 2 trumpets (D, B♭, and C); alto, tenor, and bass trombone; timpani; organ continuo; strings (violins I and II, violas, cellos, and basses); soprano, alto, tenor, and bass soloists; and soprano, alto, tenor, and bass chorus.
Like most masses, Beethoven's Missa solemnis is in five movements:
- Kyrie: Perhaps the most traditional of the mass movements, the Kyrie is in a traditional ABA' structure, with stately choral writing in the first movement section and more contrapuntal voice leading in the Christe, which also introduces the four vocal soloists.
- Gloria: Quickly shifting textures and themes highlight each portion of the Gloria text, in a beginning to the movement that is almost encyclopedic in its exploration of 3/4 time. The movement ends with the first of the work's two massive fugues, on the text "In gloria Dei patris. Amen", leading into a recapitulation of the initial Gloria text and music.
- Credo: One of the most remarkable movements to come from Beethoven's pen opens with a chord sequence that will be used again in the movement to effect modulations. The Credo, like the Gloria, is an often disorienting, mad rush through the text. The poignant modal harmonies for the "et incarnatus" yield to ever more expressive heights through the "crucifixus", and into a remarkable, a cappella setting of the "et resurrexit" that is over almost before it has begun. Most notable about the movement, though, is the closing fugue on "et vitam venturi" that includes one of the most difficult passages in the choral repertoire, when the subject returns at doubled tempo for a thrilling conclusion.
The form of the Credo is divided into four parts: (I) allegro ma non troppo through "descendit de coelis" in B-flat; (II) "Incarnatus est" through "Resurrexit" in D; (III) "Et ascendit" through the Credo recapitulation in F; (IV) Fugue and Coda "et vitam venturi saeculi, amen" in B-flat.
- Sanctus: Up until the benedictus of the Sanctus, the Missa solemnis is of fairly normal classical proportions. But then, after an orchestral preludio, a solo violin enters in its highest range — representing the Holy Spirit descending to earth — and begins the Missa's most transcendently beautiful music, in a remarkably long extension of the text.
- Agnus Dei: A setting of the plea "miserere nobis" ("have mercy on us") that begins with the men's voices alone yields, eventually, to a bright D-major prayer "dona nobis pacem" ("grant us peace") in a pastoral mode. After some fugal development, it is suddenly and dramatically interrupted by martial sounds (a convention in the 18th century, as in Haydn's Missa in tempore belli), but after repeated pleas of "miserere!", eventually recovers and brings itself to a stately conclusion.
The orchestration of the piece features a quartet of vocal soloists, a substantial chorus, and the full orchestra, and each at times is used in virtuosic, textural, and melodic capacities. The writing displays Beethoven's characteristic disregard for the performer, and is in several places both technically and physically exacting, with many sudden changes of dynamic, metre and tempo. This is consistent throughout, starting with the opening Kyrie where the syllables Ky-ri are delivered either forte or with sforzando, but the final e is piano. As noted above, the reprise of the Et vitam venturi fugue is particularly taxing, being both subtly different from the previous statements of the theme and counter-theme, and delivered at around twice the speed.
A typical performance of the complete work runs 80 to 85 minutes. The difficulty of the piece combined with the requirements for a full orchestra, large chorus, and highly trained soloists, both vocal and instrumental, mean that it is not often performed by amateur or semi-professional ensembles.
Some critics have been troubled by the problem that, as Theodor Adorno put it, "there is something peculiar about the Missa solemnis." In many ways, it is an atypical work, even for Beethoven. Missing is the sustained exploration of themes through development that is one of Beethoven's hallmarks. The massive fugues at the end of the Gloria and Credo align it with the work of his late period—but his simultaneous interest in the theme and variations form is more than absent. Instead, the Missa presents a continuous musical narrative, almost without repetition, particularly in the Gloria and Credo movements which last longer than any of the others. The style, Adorno has noted, is close to treatment of themes in imitation that one finds in the Flemish masters such as Josquin des Prez and Johannes Ockeghem, but it is unclear whether Beethoven was consciously imitating their techniques or whether this is simply a case of "convergent evolution" to meet the peculiar demands of the mass text. Donald Francis Tovey has connected Beethoven to the earlier tradition in a different way:
|“||Not even Bach or Handel can show a greater sense of space and of sonority. There is no earlier choral writing that comes so near to recovering some of the lost secrets of the style of Palestrina. There is no choral and no orchestral writing, earlier or later, that shows a more thrilling sense of the individual colour of every chord, every position, and every doubled third or discord.||”|
Perhaps the best way to recognize the importance of the mass in Beethoven's work is to acknowledge its singularity, and to view its remarkable variety and forceful individuality as the reflection of Beethoven's own relationship with the divine.
Some have remarked that his treatment of the text—including the addition of a high "a," in the Miserere section of the Gloria, and the quick disposal of several lines of text in the Credo underneath the weight of the two other choral parts and orchestra—shows a willful indifference to the more dogmatic precepts of the church, while others see the forceful expression of the central movements as having a sincerity that could only be born of true belief.