We are over half-way through the Brandenburg concerti!
The fourth concerto continues our journey through the orchestra by featuring flutes as two of the three solo instruments. As you will see in the video, Bach is referring to a Baroque flute rather than the modern flutes that we see in today’s orchestras. This flute was a type of flageolet, or tin-whistle, that was used during that time to teach pet birds how to sing. It has a very shrill and high-pitched sound that is usually at least one octave above the rest of the orchestra. Most ensembles today utilize the recorder as the closest approximation of its sound.
Despite the increased role given to the flutes, this is technically still a violin concerto. You will often hear the flutes echoing the violin solo line, which is the most difficult of all of the Brandenburg concerti. The violin will occasionally respond back, but most of the time it is leading the charge rather than following. The one exception to this is in the slower second movement, where the two flutes carry the melody for most of the movement. It is thought that the prevalence of the violin in these concerti reflects Bach’s perception of it as the closest approximation of the human voice.