In the early eighteenth century the Hanseatic city of Hamburg was not only a centre of economic development and trade, but also a political centre of the highest ranking in the Holy Roman Empire of the German Nation. Maintaining excellent diplomatic contacts thus was of primary importance for various reasons. One suitable platform for this was the opera house, which had been established in 1678 after Italian models and was the largest and best-equipped stage of this kind in Germany. Festive performances at the opera thus were used for representational occasions and exceptional socio-political events such as peace treaties, royal weddings and birthdays, or enthronements. Envoys could rent the opera house – a purely commercial enterprise and hence politically neutral – for their own functions, while the city council as Hamburg's chief representative organised festive operas whenever there was something to celebrate, particularly in connection with the Imperial House. Invitations went to diplomats residing at Hamburg, the nobility, members of the city council and other important guests and citizens. In addition, there was always a section of the general affluent public admitted to these opera performances.
Reinhard Keiser's opera Desiderius was written to celebrate the thirty-first birthday of Emperor Joseph I (26 June 1678 – 17 April 1711) and was performed on July (25 or) 26, 1709. The event took place during a period of political unrest in the city: In 1708 an Imperial commission for the restitution of order and safety had to be sent to Hamburg to quell civic upheavals against the council. Thus in 1709 the council – who doubtlessly commissioned the work – must have been especially eager to demonstrate its allegiance to the Imperial crown.
The actual background of the subject chosen for the opera was Joseph I's campaign against Pope Clement XI in the winter of 1708/1709.In order to "solve" the question whether Joseph's military measures against the Pope were justified, the librettist Barthold Feind resorted to depicting the historical campaign of Charles the Great against Desiderius, the last king of Lombardy, who was crowned in 757. The house of Lombardy ruled over a number of Italian duchies which were claimed back by Rome. But Desiderius employed skilful delaying tactics, eventually marrying his daughter Desiderata to Charles (770). Yet despite this the two ruling houses continued their hostilities, and when after the death of his brother Karlmann in 771 Charles annexed his portion of the empire, Karlmann's widow and children fled to the Lombardic court. After Charles had divorced his wife Desiderata in 772, Desiderius in 773/774 moved his army to Rome, one purpose being the anointing of Karlmann's sons as kings in order to put their territories under Lombardic rule. Pope Hadrian I turned to Charles for help, however, who first offered Desiderius compensation for the territories he had promised to return and, when this was rejected, moved his army to Italy. In 774 Desiderius had to surrender at Pavia and was imprisoned for life by Charles. With this the House of Lombardy was crushed; attempts by Desiderius' son Adalgisus to reestablish his rule met with failure.
As Charles after his victory over Lombardy had brought the Patrimonium Petri under his rule and claimed the right of investiture for himself, the subject-matter of Desiderius offered the possibility of legitimizing Joseph I's current claims against Rome. This connection is particularly emphasized by Feind in the preface to his printed libretto. The libretto itself contains only a few brief allusions, for example the occasion when Ambrose, the envoy of Hadrian I, hands over St Peter's keys to Charles, or Charles' triumphal procession to Pavia where he is hailed by Italia. Apart from this there is ample space for the kind of amorous intrigues that habitually provide the majority of the action and for which Feind leaves the firm ground of historical fact. Most of the actual reverence to Joseph is reserved for the Prologue – unusually long with its 27 numbers – and the Epilogue. The Prologue once again legitimizes Joseph's claims to sovereignty, adducing complex astrological constellations; these Feind supplements with an elaborate interpretation at the beginning of his preface.
The quality of the opera is enhanced significantly by the complex treatment of the characters in Feind's libretto. Thus Desiderius in particular has been conceived as an extremely multi-faceted figure, simultaneously comprising aspects of the king bent low under the weight of his responsibilities as a ruler, of the tyrant opposing his fate, of the hero broken by his defeat, and of the lover torn between two women. In the presentation of his characters Feind put great emphasis upon psychological motivation, which was matched especially well by Keiser's gifts of dramatization.As far as we can learn from the few sources for the years after 1710, the vocal ensemble was known to both Keiser and Feind. The surviving scores from the time show that its members were excellent singers. The Hamburg opera orchestra, too, was of unusually high quality as well as being well-equipped, so that Keiser had at his disposal excellent means for setting the Desiderius libretto to music.
Desiderius is the first modern publication of one of the celebratory Hamburg operas. The work demonstrates impressively the influence of functional concerns upon this type of composition. The extensive congratulatory Prologue has the same proportions as the opera's individual acts. Great emphasis is being put upon the display of splendour through interpolated ballets, choruses and particularly the ensemble scenes in the Prologue and Act I. Musically Desiderius is situated between Keiser's early operas with their numerous accompagnati and extended solo scenes and those of his later creative period which clearly favour the serial type. The sequence of numbers already follows mainly the recitative-aria scheme. Particularly attractive is the great variety of aria types. Keiser's musical setting matches Feind's libretto in its formal and stylistic richness. Thus after Octavia and Masaniello furioso this edition presents yet another testimony of the fruitful collaboration between Feind and Keiser.
(Hansjörg Drauschke, translation by Stephanie Wollny)