⌂ Bach's Accent steigend and Accent fallend

In the "15 Inventions and 15 Symphonies" (aka "Two- and Three-Part Inventions"), Bach uses an articulation sign, called "Accent steigend" or "Accent fallend," to indicate a grace-like note ascending or descending to the articulated note. The sign is placed about where the head of a grace note would go. It looks like a large backwards comma, or small left parenthesis. This articulation occurs in Inventio 3, shown in the third bar of the example. I defined a variable, \BachAccentFallendFromGrace that modifies an appropriately placed grace note to look like the Accent fallend. The Accent steigend should have the vertical placement adjusted slightly differently.