I've read the reference to a "Bach Bow" in a link associated with the "bow technique" inquiry made earlier as well as some on-line discussions of the subject. I just put together what I hope will be a functional bow in this style yesterday.
It seems to be the most logical first effort by any party seeking to make a violin bow who is uninfluenced by the design developed by the French bow makers of centuries's past. The bow does not have so much tension on it that one must fear the consequences if either end should slip free from the string, or the string should snap, due to high tension load, while in proximity to one's face.
The bow is easily connected to the bow hair material in a manner that enables one to relieve all tension and prevent loss of elasticity due to deformation during intervals of disuse. I have to wonder if the reason why such bows have not survived to the present is simply a matter of the Bach bow being one that would have been perceived as a "folK" bow rather than that of a professional musician during a prolonged era when support of the arts by noblemen, church aristocracy, and others with great wealth might have made them frown upon any party not using the latest and most evolved equipment. Bach was, after all, from a large, musical family in Germany. He would have likely encountered a cousin now and then who was using equipment of a cruder make than that produced in major cities. Would he not then have exploited the related possibilities?
There is also the basic assertion that a baroque bow is not a "Bach Bow" that may merit some contemplation. Why not? If a baroque bow is a curved bow under tension, as it has come to be presented today, what basis is there to assert that all bows made in that era conformed to the same level of tension and curvature? Images would not necessarily convey the type of wood, thickness, length and degree of curvature of all such bows produced in a given era. Indeed, if we take the violin bow to be modeled, to some extent, on the archery bow, nothing is more consistent than a long, relatively slim bow element that is used to create tension in a bow string. One would naturally be inclined to experiment with the amount of tension and the level of curvature of the bow for use with a muscial instrument. Is it not reasonable to question whether what we now call the modern bow or represent as the "baroque" bow is not merely the product of centuries of musical bias with regard to how a violin bow should be constructed and how a violin can and should be played?
At the same time, arguments for arpeggiating chords seem perfectly reasonable. Instruments that are strummed, such as the ukulele, produce an elegant effect when chords are arpeggiated rather than quickly strummed. Did Bach leave no instructions in this regard in his manuscripts?
