The Brandenburg Concertos are a highlight of one of the happiest and most productive periods in Bach's life. At the time he wrote them, Bach was the Kapellmeister--the music director--in the small town of Coethen, where he was composing music for the court. Since the Margrave of Brandenburg seems to have ignored Bach's gift of concertos, it's likely that Bach himself presided over the first performances at home in Coethen. They didn't have a name then; that didn't come until 150 years later, when Bach's biographer Philipp Spitta called them "Brandenburg" Concertos for the very first time, and the name stuck.
Even though he didn't call them the "Brandenburgs," Bach still thought of them as a set. What he did was compile them from short instrumental sinfonias and concerto movements he had already written. Then he re-worked the old music, often re-writing and elaborating where he saw fit. In doing so, Bach created something of a dramatic arc from the brilliant first concerto to the last, which evokes a spirited chase.
Each of the six concertos requires a different combination of instruments as well as some highly skilled soloists. The Margrave had his own small court orchestra in Berlin, but it was a group of mostly mediocre players. All the evidence suggests that these virtuosic Brandenburg concertos perfectly matched the talents of the musicians on hand in Coethen.
Just before Johann Sebastian arrived in Coethen in 1717, a new king inherited the throne in Prussia. Bach found such a rich music scene when he started to work there. It gave him the luxury of writing for virtuosos and they let him push the boundraries of his creativity. Concerto No. 2, for example, has the trumpeter play high flourishes. No. 4 allows the solo violin to soar.
Fthe Concerto No. 5 he had a real inspiration. He switched to harpsichord, gave it a knock-out part and, in the process, invented the modern keyboard concerto. The writing is so advanced and so intricate for its time that scholars assume the Fifth Concerto is actually the last Brandenburg Concerto Bach wrote.
If the dazzling writing style of the Fifth Concerto points to a late composition date, the Sixth Concerto probably came first in chronological order. It's got a simple part for the viola da gamba, a forerunner of the cello, which Bach probably put there for his employer, Prince Leopold, to play. The Prince was wealthy man and a serious music lover but probably a performer of only modest talent. The Sixth is also unique in the set because Bach omitted the violins from the ensemble; the violas take the highest string part. All six Brandenburg Concertos reveal the ebullient side of Bach, and they're one of the most welcome gifts he left us.
