While functioning as Kapellmeister (Director of Music) to the court of Prince Leopold of Anhalt-Köthen (1694 - 1728) J. S. Bach presented in 1721 to Christian Ludwig Margrave of Brandenburg-Schwedt (1677 - 1734) the Baroque masterworks known as the "Brandenburg Concertos".
This delightful performance of the orchestral works by the Freiburger Barockorchester conducted by Gottfried von der Goltz takes place in the Hall of Mirrors at the Palace of Cothen (Der Spiegelsaal im Schloss Köthen), where the great german composer himself served from 1717 to 1723.
From Wikipedia: Bach's dedication to the Margrave was dated 24 March 1721. Most likely, Bach composed the concertos over several years while Kapellmeister at Köthen, and possibly extending back to his employment at Weimar (1708--17). The first sentence of Bach's dedication reads: «As I had the good fortune a few years ago to be heard by Your Royal Highness, at Your Highness's commands, and as I noticed then that Your Highness took some pleasure in the little talents which Heaven has given me for Music, and as in taking Leave of Your Royal Highness, Your Highness deigned to honour me with the command to send Your Highness some pieces of my Composition: I have in accordance with Your Highness's most gracious orders taken the liberty of rendering my most humble duty to Your Royal Highness with the present Concertos, which I have adapted to several instruments; begging Your Highness most humbly not to judge their imperfection with the rigor of that discriminating and sensitive taste, which everyone knows Him to have for musical works, but rather to take into benign Consideration the profound respect and the most humble obedience which I thus attempt to show Him.» The dedication page Bach wrote for the collection indicates they are "Concerts avec plusieurs instruments" (Concertos with several instruments).
Bach used the «widest spectrum of orchestral instruments [...] in daring combinations», as Christoph Wolff has commented (Christoph Wolff, "Johann Sebastian Bach: The Learned Musician" (WW Norton, New York, 2000). «Every one of the six concertos set a precedent in scoring, and every one was to remain without parallel». Heinrich Besseler has noted that the overall forces required (leaving aside the first concerto, which was rewritten for a special occasion) tallies exactly with the 17 players Bach had at his disposal in Köthen (Besseler's preface to the "Neue Bach-Ausgabe" edition of the Brandenburg Concertos is reprinted with a translation in "Bärenreiter's Study Score of the Six Brandenburg Concertos", Bärenreiter TP9, 1988).
Because King Frederick William I of Prussia (1688 - 1740) was not a significant patron of the arts, Christian Ludwig seems to have lacked the musicians in his Berlin ensemble to perform the concertos. The full score was left unused in the Margrave's library until his death in 1734, when it was sold for 24 groschen (as of 2008, about US$22.00) of silver. The autograph manuscript of the concertos was only rediscovered in the archives of Brandenburg by Siegfried Wilhelm Dehn in 1849; the concertos were first published in the following year. [Malcolm Boyd, Bach: The Brandenburg Concertos (Cambridge UP, 1993)]