a very simple midi transposer (i know that to transpose midi event one can use midi keyboard splitter) but relized in this way:
you can control the transposition amount (from -12 to +12 semitones, or from -24 to +24 semitones) using TWO pushbuttons, one for increment the transposition, one to decrement it. the most important thing is that these 2 pusbottons should be remote controllable with midi CC events, so you can assign to an external surface two pusbuttons in order to raise or lower the pitch ion semitones interval.