&dAInv. 4, BWV 775, r.h.

w = ("SHORT") TRILL, m. 19: There is really no distinction between 
Bach's "short" and "long" trills: the long form often appears above 
very short notes, and the short form (as here) above extended notes 
that are clearly intended to be trilled for the full duration. It
is up to the performer to decide whether a full trill, a brief 
"inverted mordent", or something in between is most appropriate to 
the context in which the mark occurs.