Bach’s set of six unaccompanied sonatas and partitas for the violin represent the unchallenged peak in solo violin music, both in technique and in expressive variety. The three sonatas follow the four-movement sonata da chiesa pattern, while the three partitas include dance forms. Each sonata has a fugue as its second movement, and in each case this is not only a tour de force, since fugal writing presupposes the participation of three or more voices, but also the dramatic and emotional core of the sonata. All these works require extraordinary skill in double-, triple-, and quadruple-stopping, as if the violin were an instrument with the same potential for chords and harmony as a harpsichord or an organ.

The Second Sonata, in A minor, opens with an improvisatory Grave which leads directly into the fugue, a movement which allows flowing episodes between the strictly fugal passages, where Bach’s invention is at its incredible best.

The Andante offers a flowing melody over a steady bass line (unbroken eighth-notes) in the manner of a Vivaldi concerto. A third and a fourth voice enter from time to time to enrich the harmony. The Allegro finale leaves chords behind and adopts the conceit of perpetual motion, with some considerable use of echo effects.

Bach was not the only composer of his time to write for solo violin, but he far outstrips his contemporaries in this domain, as in so many others. It is likely that he wrote them during his time in Cöthen around 1720 and that he had a particular violinist in mind. Although celebrated as an organist, Bach could also play the violin; it’s a fair guess that he could play these pieces pretty competently himself.

Hugh Macdonald is Avis Blewett Professor of Music at Washington University in St. Louis. He has published books on Scriabin and Berlioz, and his book of essays Beethoven’s Century appeared in 2008.