The Capricio in A, written on folio 27 of manuscript Am.B 340 bears the intials "B.M.". It is unknown which composer is meantby these initials. As Karges was familiar with the circle of Sweelinck students, it is intruiging to note that one of the composers in Ms Lynar B3 is designated as "M.W.C.B.M." (see for two sompositions designated to this composer: http://partitura.org/index.php/m-w-c-b-m/
). An unlikely theory, put forward by Max Seiffert was that these initials could stand for “Magister Wilhelm Carges Berolinensis Marchicus” (Master Wilhelm Karges of Berlin and the Mark), meaning that this work was written by Wilhelm Karges himself. We can safely discard that theory. However, since initials were perhaps not per se surnames of christian names, the question is whether "M.W.C.B.M" from Ms Lynar B3 could be the same person as "B.M." from Am.B 340. And that's a question we will probably never know an answer to.
The Capricio this B.M. wrote was probably heavily edited by Karges and it is an enigma how much of this music is from B.M. and how much is from Karges. It is nevertheless a nice chromatic piece that is great to play. If Karges edited the original in to this form, he did a nice job.
Score available here: http://partitura.org/index.php/wilhelm-karges-b-m-capricio-in-a