Duke Johann Ernst of Saxe-Weimar, the young nephew of the aristocrat in whose chapel J.S. Bach was organist from 1708 to 1717, was also a keen music student who spent much time and energy improving himself as a player of the violin and as a composer. So it makes perfect sense that Bach, when he was arranging for solo organ six concertos by other composers (BWV 592 - 597, the last of which may be inauthentic), included two concertos composed by the Duke among his source works. (Sadly, the Duke died while still a teenager, so both his musical and his political powers remained essentially untapped.) The second of the organ concertos based on the Duke's music is the single-movement Concerto for organ No. 4 in C major, BWV 595; it takes a violin concerto in the same key by Duke Johann as its starting point, and is the shortest of the organ concertos (and the only one in a single movement). Ernst's original has not been found. The main ritornello theme is repetitive and simple, moving over the same few notes, and the episodes keep the same semiquaver rhythmic figure throughout the entire piece. The frequent manual changes, however, do hold the listener's interest.

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