The six Brandenburg concertos (BWV 1046-1051) by Johann Sebastian Bach are a collection of instrumental works presented by Bach to the Margrave of Brandenburg in 1721, but probably composed earlier.

Table of contents
1 History
2 The concertos: orchestral vs. chamber music
3 The individual concertos
4 Other

History

By 1721, Bach's third year as Kapellmeister at Anhalt-Cöthen, he was becoming restless and began looking for career opportunities outside the small town. In March, he assembled these six concertos (which has almost certainly been performed at Cöthen) and presented them, by way of a job application, to the Margrave of Brandenburg. (The application was not successful.)

The concertos have little in common; the dedication page Bach wrote for the collection merely indicates they are six pieces for several instruments. Indeed, the six works attempt to use as many different combinations of common instruments as the composer could think of. The concertos have been called a "microcosm of Baroque music," because they seem to exemplify the potentials of the musical style of the era, in all its variety—in only six concertos.

The concertos: orchestral vs. chamber music

In modern times these works have been performed by chamber orchestras, using a fairly substantial string section. However, they have also be performed as chamber music, with just one instrument on each part. The very small size of the orchestra in Bach's day means that the distinction between the two approaches would not have been very significant at that time.

A minor detail about the Fifth Concerto indicates something about the size of the forces with which they were originally performed. This concerto (see below) features a harpsichord solo, which was almost certainly performed by Bach himself. It also lacks a second violin part. The best explanation of this goes as follows. We know that when playing in the string section, Bach preferred to take the viola part; according to a surviving letter, this was so he could sit "in the middle of the harmony." Since as keyboard soloist Bach wasn't available to take the viola part for this concerto, one of his violinists must have had to move over to play the viola. The explanation, of course, relies on the assumption that Bach's ensemble used only one musician per part.

What we will probably never know is whether, had Bach worked in a wealthier musical establishment, he would have wanted to assign more musicians to the string section; this remains a choice that modern performers are free to make.

The individual concertos

Brandenburg Concerto #1 in F major

 I.   (Allegro)
 II.  Adagio
 III. Allegro
 IV.  Menuetto; Trio I; Polacca; Trio II

The First Concerto in F major calls for two French horns, three oboes, a bassoon, and a violino piccolo as well as two violins, a viola, and a basso continuo for accompaniment. This concerto is the only one in the collection of six with four movements, rather than three. The last movement is an extensive and relaxed sequence, consisting of a minuet played four times, with a separate trio or polacca section for each of the intervals. An earlier version of this concerto survives as a sinfonia, BWV 1046a.

Brandenburg Concerto #2 in F major

 I.   (Allegro)
 II.  Andante
 III. Allegro

This is in the form of a concerto grosso, and calls for a somewhat simpler but rather unusual ensemble of trumpet, recorder, oboe, and solo violin, with two violins, a viola, and a basso continuo again accompanying. Scholars today continue to be astonished that the trumpeter in Bach's ensemble was able to handle the rapid passagework of this part while playing an instrument that had no valves. Even today, when a special valved piccolo trumpet is often used, the part is considered very demanding.

Brandenburg Concerto #3 in G major

 I.   (Allegro)
 II.  (no tempo mark)
 III. Allegro

This concerto is often cited as the prototype of the modern string quartet as Bach here calls for only stringed instruments. The three violins, three violas, and three cellos are accompanied by a basso continuo. The second movement consists of only two chords played by the strings; it is likely that these chords surrounded or followed a cadenza improvised by a keyboard or violin player.

Brandenburg Concerto #4 in G major

 I.   (Allegro)
 II.  Andante
 III. Presto

This concerto—for violin and two recorders accompanied by two violins, a viola, and a basso continuo—uses these common instruments in uncommon ways; the demanding solo violin part mimics the continuo accompaniment at times, moving what is traditionally foundation to the treble register. In modern performances flutes are sometime substituted for recorders.

Brandenburg Concerto #5 in D major

 I.   Allegro
 II.  Affectuoso
 III. Allegro

This concerto was written for flute, violin, and harpsichord, with violin, viola, and basso continuo support. It makes use of a popular chamber music ensemble configuration (flute, violin, and harpsichord). It is believed that the concerto was written in 1719, shortly after Bach had brought back from Berlin a new harpsichord for the Cöthen ensemble. The concerto is well suited throughout to showing off the qualities of a fine harpsichord, but especially in the lengthy and flamboyant solo cadenza to the first movement. It seems almost certain that Bach, considered a great keyboard virtuoso in his day, was the keyboard soloist at the premiere. Scholars have seen in this work the origin of the virtuoso keyboard concerto, developed later in Bach's own work as well as in the piano concerti of Mozart and Beethoven.

Brandenburg Concerto #6 in B flat major

 I.   (Allegro)
 II.  Adagio ma non tanto
 III. Allegro

This concerto sets two trio groups against each other. On one side sit the "modern" instruments: two violas and a cello, while on the other are the "old-fashioned" violas da gamba and double bass. These opposed low-register trios present a series of call-and-response motifs.

Other

The Brandenburg concertos, especially the Second, Third, Fourth, and Fifth, continue to be very popular to this day and are frequently performed and recorded. Generally, mainstream symphony orchestras play them less often than in the past, and the works are now more often the province of authentic performance ensembles.

As with other familiar works of classical music, the Brandenburg Concertos have repeatedly been mined for use in film scores and as theme music for television programs.