Your accordion, after having been MIDI’d, becomes a MIDI controller !
This is all beginning to make sense now !
Generally, a MIDI controller doesn’t emit any sound !
But, here’s where the accordion is different … we’ve still got acoustic reeds !
Unless it’s a reedless accordion … in which case the only sound it will make is when you hit it with some drumsticks !
The accordion with it’s installed digital interface sends out pure MIDI data that has to be interpreted by the expander.
The original idea for MIDI in the first place, was to allow musicians to be able to control several electronic instruments from one device.
So, your expander is sitting there waitjing for MIDI messages from the accordion telling it what instrument sound to play !
Bagpipes from the accordion … easy !!