The Harpsichord Concerto in A major, BWV 1055, is a concerto for harpsichord and string orchestra by Johann Sebastian Bach. It is the fourth keyboard concerto in Bach's autograph score of .
History
Unlike Bach's other harpsichord concertos, BWV 1055 has no known precursors, either as an instrumental concerto or as a movement with obbligato organ in a cantata. It has generally been accepted that it is a reworking of a lost instrumental concerto, since Donald Francis Tovey first made the suggestion in 1935, when he proposed the oboe d'amore as the melody instrument. Additional reasons for the oboe d'amore have been given by Ulrich Siegele in 1957, Wilfried Fischer in 1970, Hans-Joachim Schulze in 1981 and Werner Breig in 1993; Schulze has dated the original concerto to 1721; and a reconstruction as a concerto for oboe d'amore and strings was prepared by Wilfried Fischer in 1970 for Volume VII/7 of the Neue Bach-Ausgabe edition. Another proposed instrument has been the viola d'amore, first suggested by Wilhelm Mohr in 1972; additional reasons for choosing the viola d'amore as a possible melody instrument were later given by Hans Schoop in 1985 and Kai Köpp in 2000, but in 2008 Pieter Dirksen gave reasons why he considered it unlikely to have been the original melody instrument.
Structure
Scoring: harpsichord solo, violin I/II, viola, continuo (cello, violone)
First movement
As explains in his preface to the Neue Bach-Ausgabe edition, in compositional terms, BWV 1055 is one of the most concentrated and mature of Bach's concertos. The opening movement is an Allegro in A major and . It is written in da capo A–B–A′ form. Mostly light and nimble in spirit, the movement starts with a 16-bar ritornello broken up into two halves, each 8 bars long. In the first solo episode, the harpsichord introduces its own more sustained thematic material as well as semiquaver passagework derived from the end of the second half of the ritornello. All the harpsichord solo passages are based on or develop this thematic material.
The two bar "motto" or Vordersatz opening the ritornello, consisting of rhythmic spiccato quaver figures in the strings and cascading broken chord semiquavers in the harpsichord, recurs throughout the movement, heralding solo episodes for the harpsichord. In the remainder of A section, the second episode is introduced by the two bar motto and followed by a reprise of the entire first half of the ritornello. Section B starts with an 8-bar solo episode and has three more solo episodes, punctuated by the two-bar ritornello motto. In the second bar of the first episode the sustained harpsichord material is heard in counterpoint to the motto theme in the strings, now starting in the middle of a bar. The second and third episode are 6 bars long in E major/F minor and B minor/C minor. The fourth and longest, which ends section B, is 12 bars long, starting in C minor and ending back in the tonic key of A major. Section A′ starts at bar 79 with what sounds like a reprise of the ritornello—the two-bar motto in its original key; but, as Bach did in many of his concertos, it is interrupted by a solo episode for harpsichord—a variant of the episode introducing section B—before the true reprise of the complete ritornello that concludes the movement.
Second movement
The slow movement of BWV 1055 is a highly expressive Larghetto in F minor and time. Although it does not have the dotted rhythms of a siciliano, it is close in spirit to this melancholy dance-form. The movement is pervaded by the chromatic fourth—both falling and rising—which is associated with the lamento. It is first heard in the descending bass line of the opening two bar ritornello, which frames the work. The material between the opening and closing the ritornellos is freely developed, but nevertheless has some elements of sonata form, most significantly a division into two parts with the second part starting in the relative major key (bars 3–13 and bars 14–36).