Bach's Fantasia in C major for organ, BWV 570 is an early work, probably composed sometime during the composer's tenure as organist in the city of Arnstadt (1703 - 1706) or perhaps during his one year at Mühlhausen (1707). It is one of the few of Bach organ fantasias/organ preludes that do not belong to larger, two-part prelude-fugue or fantasia-fugue combinations; it was only with his move to Weimar, in 1708, that Bach really began to fancy such compound prelude-fugue works, though he did compose a few famous examples of them before the Weimar days (including the Toccata and Fugue in D minor, BWV 565).

BWV 570 is written in four voices to be played on two manuals without pedals. Because of this it can be (and has been) played on other keyboard instruments—but not, it must be pointed out, to good effect, since a great deal of the piece is built around sustained tones that die all too quickly on the harpsichord or piano. Both the careful harmonic plan and the general trend of rhythmic motion—spacious opening rhythms gradually growing more dense and active as the note values grow smaller and the motivic imitation accelerates—presage stylistic hallmarks of Bach's mature keyboard works.

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