The 18th composition from manuscript Becker III.8.63 is a prelude in B flat major. It is a nice play with the motif introduced in bars two and three. The prelude wanders up and down the circle of fifths, thus giving it structure. The prelude starts in B flat major (obviously) and subsequently touches the tonalities of F major, d minor, g minor, c minor, f minor, E flat major, c minor, g minor and back to B flat major. The final bars are a long dominant section before the pece concludes on a B flat major chord.