The Brandenburg Concertos by Johann Sebastian Bach (BWV 1046–1051, original title: Six Concerts à plusieurs instruments) are a collection of six instrumental works presented by Bach to Christian Ludwig, Margrave of Brandenburg-Schwedt, in 1721 (though probably composed earlier). They are widely regarded as some of the best orchestral compositions of the Baroque era.
No. 6 in B♭ major, BWV 1051
Title on autograph score: Concerto 6to à due Viole da Braccio, due Viole da Gamba, Violoncello, Violone e Cembalo.
- [no tempo indication, alla breve] (usually performed at Allegro or Allegro moderato)
- Adagio ma non tanto (in E♭ major, ends in an imperfect cadence of G minor)
Instrumentation: two viole da braccio, two viole da gamba, cello, violone, and harpsichord
Duration: about 16 minutes
The absence of violins is unusual. Viola da braccio means the normal viola, and is used here to distinguish it from the viola da gamba. When the work was written in 1721, the viola da gamba was already an old-fashioned instrument: the strong supposition that one viola da gamba part was taken by his employer, Prince Leopold, also points to a likely reason for the concerto's composition—Leopold wished to join his Kapellmeister playing music. Other theories speculate that, since the viola da braccio was typically played by a lower socioeconomic class (servants, for example), the work sought to upend the musical status quo by giving an important role to a "lesser" instrument. This is supported by the knowledge that Bach wished to end his tenure under Prince Leopold. By upsetting the balance of the musical roles, he would be released from his servitude as Kapellmeister and allowed to seek employment elsewhere.
The two violas start the first movement with a vigorous subject in close canon, and as the movement progresses, the other instruments are gradually drawn into the seemingly uninterrupted steady flow of melodic invention which shows the composer's mastery of polyphony. The two violas da gamba are silent in the second movement, leaving the texture of a trio sonata for two violas and continuo, although the cello has a decorated version of the continuo bass line. In the last movement, the spirit of the gigue underlies everything, as it did in the finale of the fifth concerto.