The Concerto, BWV 525a (alternatively: BWV deest), is a trio sonata in C major for violin, cello and basso continuo, based on material otherwise found in Johann Sebastian Bach's first Organ Sonata, BWV 525 (outer movements), and Flute Sonata in A major, BWV 1032 (middle movement).
[1] The oldest extant manuscript containing the BWV 525a arrangement, D-B Mus.ms.
[2] Although this version of Bach's sonata movements may have originated during his lifetime in the circle around him, it seems unlikely that the composer supervised, or even ordered, the manufacture of the string trio adaptation, thus the arrangement has been listed in BWV Anh.
of doubtful works, in the 1998 edition of the Bach-Werke-Verzeichnis (BWV).
[4] Digital facsimiles of 18th- and 19th-century manuscript copies of the arrangement, in which the sonata is titled "Concerto", became available in the 21st century.