This is Bach’s own transcription of his Fourth Brandenburg Concerto. It appears in the manuscript from 1737-9 of all seven of his harpsichord concertos. The Brandenburg Concertos themselves date from 1721, during his days in Köthen. He obviously liked his Fourth Concerto, deciding to re-score it for this series. Bach gave the harpsichord the original part for the violin with some embellishments and also modified the original recorder parts (described as “fiauti d’echo” in the Brandenburg Concerto) and added some material for the other instruments. The key was also changed to suit the harpsichord. It opens with an enchanting, swinging theme presented by the recorders . The harpsichord soon adds busy, running phrases and these elements provide the basic material for the movement. First the recorders elaborate on their theme, then the harpsichord is given its opportunity in a flowing sequence, with occasional comments from the others. The recorders return for repeats of the opening theme or ritornello, interspersed with delightful variations for the harpsichord. As always Bach knows just how long to develop his material and with a further visit from the ritornello this delightful movement comes to a well-timed stop.
There is a strong feeling of a sarabande about the slow movement, the stately Spanish dance so popular in Baroque suites. The soloist launches a gently sighing melody, with echo repeats on the recorders marked piano. This is expanded gracefully with attractive recorder descants and further echo effects, with a final recorder flourish as the music comes to an end. The finale is a vigorous contrapuntal creation. The opening theme is treated to many felicitous variants. There is a great driving force to the whirling tempo and vibrant phrases that is most uplifting and refreshing; it is Bach at his finest.