I've asked for this type of utility a few times
before. Qmidiroute
and midirgui do some of what I've asked for but no stand-alone app
does what the Yamaha MEP4 did, i.e., rechannelize, convert from one
controller type to another, value scaling, event filtering, etc. It
seems like these functions should be rather easy to add to an app
like midirgui. I think most of the math is simple integer stuff.
using Qt4 and RtMidi, it should be easy to create such an app. You
"only" need someone who has the time to do it :) .
Best regards
ce