The Brandenburg concertos are six concerti grossi that Bach wrote as a gift for the Margrave of Brandenburg, a nobleman that Bach was hoping to impress in order to obtain employment in his court (he didn’t get the job).  This link will take you to an article at National Public Radio detailing the origins of these concertos, widely considered to be among the greatest orchestral compositions of the period.  Remember that while this article discusses all six concertos, the piece on our playlist is the 1st movement from Concerto No. 5 in D major.  You can also visit the Wikipedia page on the Brandenburg Concertos where you can listen to all six works in their entirety.