Johann Sebastian Bach was thirty-two when he assumed the position of Kapellmeister at the Court of Prince Leopold of Anhalt in Cöthen, in December 1717. It was a big decision for the composer, who already had a perfectly good job as orchestra leader for the Duke of Weimar, where he had worked since 1708. Accepting the new position was personally disruptive quite beyond moving Bach's quickly growing family the distance of about sixty miles; the Duke refused to accept Bach's resignation, and had him held under arrest for a month before he finally relented and let his orchestra leader go.

But the allure of Cöthen was substantial. Leopold's realm may have been small (with just 5,000 subjects), but his passion for music was boundless. He was himself a reasonably accomplished performer on the viola da gamba and he traveled to France, England, Italy, and the Netherlands to polish his skills not only as a gambist, but also as a violinist and harpsichordist. As a teenager the Duke had convinced his mother to start hiring a musical staff with whom he could play chamber music when he was at home in Cöthen, and by the time he assumed the throne himself, the assemblage had grown into a full-fledged Collegium Musicum -- essentially an orchestra. As it happened, Fredrich Wilhelm I, the King of Prussia, had just then reallocated his resources to put more money into military spending, and as a result Leopold had his pick of the newly unemployed players who had played in the King's orchestra.

What Prince Leopold could offer Bach was a professional ensemble of three violinists, a cellist, a bassist, two flutists, an oboist, a bassoonist, two trumpeters, a timpanist, an organist, and three singers -- and their numbers might be swelled by several amateur musicians who held other positions at his court. Because Prince Leopold adhered to the Reformed faith, his church services didn't require elaborate music; that freed up his music director to spend most of his time writing secular instrumental pieces such as sonatas, concertos, and orchestral suites.

Many of Bach's most buoyant instrumental works date from his years at Cöthen, including his Brandenburg Concertos and his violin concertos. The exact dating of these works is often problematic, since most of Bach's Cöthen manuscripts are lost. The Brandenburg Concertos appeared as a collection of six discrete works, and they were, at least in part, Bach's arrangements from earlier settings. The collection was assembled as a sort of job application. In 1721, Bach was in his fourth year as Prince Leopold's musical director when the Prince married a woman who did not share his musical interests, and the court's musical life immediately took a plunge. On March 24 of that year, the composer, three days past his thirty-sixth birthday, inscribed a servile dedication letter in courtly French to the Margrave of Brandenburg, whom he had met a couple of years before, and who Bach felt might be interested in hiring him. The letter -- and the six concertos that accompanied it -- seem never to have been acknowledged, and it is all but certain that the Margrave of Brandenburg never had the works performed. Possibly, he couldn't have, since they call for the instrumental forces of Anhalt-Cöthen, which considerably surpassed those then in place at the Margrave's palace. Nonetheless, the name Brandenburg became attached to them many years later.

Each of the six Brandenburg Concertos has a distinct character and employs a different combination of instruments. In general, the Third Brandenburg Concerto, along with the First and the Sixth, can be taken to exemplify the emerging sense of what we recognize in retrospect as an orchestral style, stressing the blend of instrumental sections; these are concertos in the sense that the word was employed in the Baroque to mean a "coming together" of instruments. In contrast, the Fifth Brandenburg Concerto stands with the Second and Fourth as celebrating - -- even exploiting - -- sheer instrumental virtuosity. Since even the "historically informed" performance of Baroque music is growing increasingly more emotive and Romantic, it will perhaps not be out of place to quote a wise and heartfelt observation by the humanitarian, physician, organist, and Bach biographer Albert Schweitzer, writing in 1905 on the subject of the Brandenburg Concertos:

"Bach takes up the ground idea of the old concerto, which develops the work out of the alternation of a larger body of tone -- the tutti -- and a smaller one -- the concertino. Only with him the formal principle becomes a living one. It is not now a question merely of the alternation of the tutti and the concertino; the various tone-groups interpenetrate and react on each other, separate from each other, unite again, and all with an incomprehensible artistic inevitability. The concerto is really the evolution and the vicissitudes of the theme. We really seem to see before us what the philosophy of all ages conceives as the fundamental mystery of things -- that self-unfolding of the idea in which it creates its own opposite in order to overcome it, creates another, which again it overcomes, and so on and on until it finally returns to itself, having meanwhile traversed the whole of existence. We have the same impression of incomprehensible necessity and mysterious contentment when we pursue the theme of one of these concertos, form its entry in the tutti, through its enigmatic struggle with its opposite, to the moment when it enters into possession of itself again in the final tutti."

The Brandenburg Concerto No. 3 is for an expanded string orchestra without any soloists. It is cast in only two fast movements connected by a pair of modulatory chords (Adagio). It seems likely that the "missing" middle movement was meant to exist all the same, quite likely in the form of an improvisation by the continuo harpsichord, or perhaps by more than one of the assembled instrumentalists, and that the concluding chords are merely shorthand clarifying what the improvisation's closing harmonies should be.