I'd go with 9 Kleine Präludien aus dem Klavierbüchlein für Wilhelm Friedemann Bach
vhttp://imslp.org/wiki/9_Kleine_Pr%C3%A4ludien,_BWV_924-932_(Bach,_Johann_Sebastian) . On playing, I find the set of 12 to be a spurious thing.
Here's an interesting comment:
Bach's authorship of Nos.3, 8 and 9 is doubtful (possibly composed by Wilhelm Friedemann Bach)