Emacs' mouse event code deals with the up- modifier (bit 0 in the modifier mask) by converting it to click- or drag-events. This happens at the C level. However, when synthesizing events for things like Midi keyboards (basically computerized music instruments), it makes sense _not_ to convert an up-key event to either a drag or click event since usually the down-event is a principal event of its own: basically the "importance relation" of down- and up-events is reversed for those kinds of keys as compared to mouse buttons and this reflects in what kind of event one would want representing it. This patch allows the keymap machinery to treat the up- modifier in a manner analog to the down-modifier even though Emacs will not (yet) natively generate up-events itself. However, it will allow sensible behavior for such events being pushed into unread-command-events. It has been proposed on the Emacs developer list on and had some comments amended at . However, there was an additional request at to change one comment in read_key_sequence to actions not matching the code in read_key_sequence but rather happening in make_lispy_event. The explanation why this change would be inappropriate in was after an additional exchange "resolved" with an ad hominem attack in . Further private communication led to no results. In order to at least provide users in need of this functionality with a referenceable issue report (and possibly get someone else to apply the patch), I am submitting the patch against current master here.