Mainstage 3.2.3: no MIDI output to external devices

I want to use Mainstage to control Program Changes in my hardware keyboards via MIDI and have defined a concert and a number of patches as devised in the instructions in the manual (started from scratch, defined channel strips for external devices etc.).

There is no MIDI output however. I threw in a couple of MIDI activity lamps but they don't light up when I select a patch (they do light up if I press a key on one of the keyboard images on the workspace screen). Conversely, I connected MIDI in from one of the external keyboards and immediately got a response when I played the (real) keys.

Maybe I am missing the point, but it was my impression that the selection of a patch should invoke an outbound program/bank change to be transmitted?

The setup: Macbook Air (OS/X 10.9.5) --USB-- Roland Quad-Capture MIDI and Sound interface --MIDI-- Nord Electro 3HP, Nord Wave, Roland JV2080.

Any hints would be greatly appreciated.