docs: def _message_callback(self, msg):
          """Callback function to handle incoming MIDI messages."""
          if msg.type == 'polytouch':
              button = button_from_press(msg.note)
              if button:
                  self.on_button(button, msg.value != 0)
              elif msg.note == 127:
                  self.on_fader_touch(msg.value != 0)
          elif msg.type == 'control_change' and msg.control == 0:
              self._msb = msg.value
          elif msg.type == 'control_change' and msg.control == 32:
              self._fader = (self._msb << 7 | msg.value) >> 4
              self.on_fader(self._fader)
          elif msg.type == 'pitchwheel':
              self.on_rotary(1 if msg.pitch < 0 else -1)
          else:
              print('Unhandled:', msg)