Thanks a lot ! The MS40 sounds like a good option, but I'd really like something lightweight (7kg versus 0.9 kilos for the SD4 for example).

mmmh not sure it actually exists, even the SD4 is apparently not usable with a footswitch (although there's a modified version here that does it: http://scotlandaccordions.co.uk/MIDI%20Expanders/Ketron%20SD4%20with%20control%20pedal).

Any other inputs on lightweight sound modules usable with footswitch for accordion ?

Thanks !