The original source of this piece in manuscript Am B 340 is a manualiter Toccata by Heinrich Scheidemann. The practical source is a manuscript in which Scheidemann's piece was reworked into a pedaliter piece, significantly shorter (186 versus 115 bars) and with a lot of material not present in Scheidemann's original. Karges (?) reworked this adaptation into an again shorter work of only 55 bars. Karges adds no new material (except for the last three bars), he just cuts out the middle part. The result is a work that is for the first half based on the original of Scheidemann, and for the second half on the adaptation of an unknown scribe. The result is a concise piece, that builds from a relatively slow pacing start, via some surprising chromatic echo effects to a satisfactory conclusion.
Manuscript Am.B. 340, as a source of works by Scheidemann or Sweelick or others, has been called "utterly unreliable". Nevertheless, the result is "highly enjoyable".
Score available here: wilhelm-karges-heinrich-scheidemann-fantasia http://partitura.org/index.php/