Pad 14 is inactive in MIDI Keyboard Mode, while 15/16 act as transpose buttons. It would be nice if pad 14 played the next note up from pad 13, as I'm finding myself frequently wishing it was there while playing. In a perfect world, 15 and 16 would also play notes, while the transpose function is moved to perhaps the NAV buttons.
But if nothing else, pad 14 should play a note.