"We hear from Potsdam that last Sunday, May 7, 1747, the famous Capellmeister from Leipzig, Bach, arrived with the intention of hearing the excellent Royal music. In the evening, at about the time when the regular chamber music in the royal apartments usually begins, his Majesty was informed that Capellmeister Bach had arrived at Potsdam and was waiting in His Majesty’s antechamber for His Majesty’s most gracious permission to listen to the music. His August Self immediately gave orders that Bach be admitted, and went, at his entrance, to the so-called Forte-and-Piano, condescending also to play, in person and without any preparation, a theme to be executed by Capellmeister Bach in a fugue. This was done so happily by the aforementioned Capellmeister, that not only His Majesty was pleased to show his satisfaction, but also all those present were seized with astonishment. Bach has found the subject propounded to him so exceedingly beautiful that he intends to set it down on paper in a regular fugue and have it engraved on copper."
In these words the Spenersche Zeitung of Berlin in its issue of May 11, 1747, apprised its readers of the visit of Johann Sebastian Bach (1685-1750) at the palace of Frederick the Great of Prussia. On that famous occasion the King, who was an excellent musician, played for Bach on the piano a fine tune of his own invention, containing both diatonic and chromatic elements, and asked him to improvise a fugue on it.
Bach’s response is history. Upon his return to Leipzig, he expanded his improvisation by writing a magnificent “Musical Offering,” a cornucopia of learned devices comprising a mirror canon, imitation in contrary motion, a crab canon (with the Royal Theme played backwards), and culminating in a magnificent Ricercar, in six voices. Bach’s marginal remarks in the manuscript are most revealing of the traditional obsequiousness to ruling sovereigns of the time. To illustrate the augmentation, in which the thematic notes assume double value, Bach writes: “As the notes augment, so may the King’s fortune grow.” At the change of the key, Bach submits, “As the modulation rises, so may rise the glory of the King.” There is also a riddle canon, with the Latin motto “Quaerendo invenietis” (by seeking you shall find out), in which the performer must find the proper place and form of the entries. The request is not simple since the imitation is to be made in inversion. Bach entitled his “‘Musical Offering” Ricercar, in the form of an acrostic: Regis Iussu Cantio Et Reliqua Canonica Arte Resoluta (At King’s Command Theme and Additions by Canonic Art Resolved).
The term Ricercar, or Ricercare, literally “to research,” was originally applied to the “searching” of correct intonation on a string instrument, in other words, tuning. By a semantical extension it came to signify the seeking of the tonality of the principal part of the work, a preamble or a prologue. Through further differentiation, the Ricercar developed into a full-fledged fugal exposition, and the terms Ricercar and Fuga became interchangeable. Bach’s “Musical Offering” is indeed a manifestation of the highest art of the fugue.
Anton von Webern (1883-1945), who adapted his great polyphonic skill mainly to dodecaphonic techniques, had profound reverence for the great masters of the Baroque art, and particularly for Bach, and approached the task of orchestrating the concluding portion of Bach’s Ricercar with great fidelity to the spirit of the music. But he believed, as did his revered teacher Arnold Schoenberg, that classical music must be arranged in terms of modern instrumental ideas. In his orchestration, Webern used a flute, oboe, English horn, clarinet, bass clarinet, bassoon, horn, trumpet, trombone, harp, and strings. The opening notes of the Royal Theme are given to the muted trombone, and the rest of the subject is allotted to muted horn and muted trumpet. This overlapping of instruments is fashioned after the medieval hocketus (literally, hiccup), an effect created by a deliberate discontinuity of a melody.
Expression marks and tempo indications in Webern’s score are noteworthy: zart fliessend, fliessender, sehr fliessend, rubato. Who would think that an ultra-modernist like Webern, arranging the music of Bach, would ask the players to perform tenderly, flowingly, more flowingly, and in free measure? In this instance, classicism and modernism suddenly turn romantic.
— Nicolas Slonimsky