A group of the instrumental sonatas J.S. Bach composed while living and working in Cöthen during the late 1710s and early 1720s -- specifically, the six sonatas for violin and harpsichord, the three for viola da gamba and harpsichord, and two of the four authentic flute sonatas -- are especially and rightfully famous for one thing: in these 11 works, by writing out a full harpsichord part on two staves rather than merely writing a bass line and figured bass, Bach promoted the harpsichord from mere continuo foundation to true equal of the solo instrument. Although not as famous as the six Sonatas and Partitas for solo violin, the above-mentioned sonatas for violin and harpsichord are among Bach's most famous chamber pieces; it is possible, assuming that Bach in fact composed it before the other five, that the first of these sonatas, BWV 1014 in B minor, is in fact history's very first modern duo sonata.
The Sonata for violin and keyboard No. 1 in B minor, BWV 1014, falls into four movements that follow the usual slow-fast-slow-fast plan of the Baroque sonata da chiesa, but within that loose framework Bach, as usual in his sonata works, explores diverse forms such as those of the aria and the concerto. The opening Adagio is a rich essay in 6/4 time in which the harpsichord offers an idea built from an arpeggiated bass line and pungent groups of eighth notes in parallel thirds and sixths, and the violin provides an obbligato line whose long-sustained tones invariably taper off into ornate tails that dip and duck into the next phraselet. The following Allegro is an example of that peculiar chamber movement species of which Bach was so fond and which he alone brought to perfection: a full synthesis of dense fugal style, Baroque concerto form and trio sonata part-writing. The movement is in three clear sections (ABA'), with the opening bars returning to usher in the final third of the movement.The third movement, in D major, is a sumptuous Andante in which the two upper voices -- the harpsichord's right hand and the violin -- generally move in counterpoint with one another but come together for a gorgeous subsidiary idea in parallel thirds. The finale is an Allegro whose two main ideas -- a trumpet-like, repeated-note notion and a running sixteenth-note counterpoint to that idea -- are built up into a true binary design complete with repeat signs.