Orchestral and Chamber masterpieces
Today we would call Bach a "man-orchestra". He could play many instruments very well, he knew their possibilities and could perfectly take advantages of this knowledge composing his pieces. Bach's instrumental music is joyful, not boring, one could even say it is a kind of entertainment music. Compositions created during the period when he was a conductor in Köthen belong to it. In comparison with other pieces composed by Bach, this type of music is easy to listen to... although not easy to play. Bach could work with orchestra from 1717 during his stay in Köthen and then in Lipsk, where from 1729 to 1737 and still from 1739 to 1741 he took over the management of Collegium musicum founded by Telemann. Most of his instrumental compositions was created during this time.
The term "Orchestra" during the times of Bach referred rather to a bigger group of musicians, rather than to a philharmonic orchestra that was created in 19th century. However, these were these smaller orchestras that contributed to the proper reception of Bach's music.
In Köthen a collection of six Brandenburg's concerts was created. They reveal Bach's penchant for experiments. He used a different set of instruments in every concert thanks to which he achieved incredible effects.
Equally famous Suites for orchestra are believed to heave been composed in Lipsk (BWV 1066-1069). They are rather based on the French trends of stylised dance compositions. The earliest (BWV 1066) might have been composed in about 1725, and the latest h-moll suite (BWV 1069) with the masterly part for the flute in about 1739. It is at the same time the latest Bach's composition for orchestra.
Finally the solo concerts belong to this genre. These concerts were composed during the 1730s through elaboration and transposition of his previous compositions, for example love oboe concerts (BWV 1055) or violin concerts (BWV 1054 from 1042, 1057 from 1049 and 1058 from 1041). To the same extent as the V Brandenbrurg's concert constitutes the beginning of music for key instruments and other ones, the harpsichord concert can be regarded as the prototype of piano concerts.
"To strip human nature until its divine attributes are made clear, to inform ordinary activities with spiritual fervour, to give wings of eternity to that which is most ephemeral; to make divine things human and human things divine; such is Bach, the greatest and purest moment in music of all time.".
Pablo Casals, spaine cellist and composer (1876-1973)