I was looking up some tarantella music online and ran across this
Tarantella Accordion Solo, Roland FR-7
which made me look here
Roland FR-18 Diatonic V Accordion - Black
and here Roland FR-18 diatonic V-Accordion® - Boni Mauricio Demo
How can something be entirely digital and need to use the air power of a bellows? Is the air power power actually doing any work producing music on this organ or is the bellows just for show?
Reading the specs in that second link, it appears that the bellows work mechanically along with a digital pressure sensor. In a real accordion, volume is controlled by varying pressure on the bellows (going by memory of my mom playing), and there are a number of other effects as well, like ‘bending’ notes and getting more or less ‘reed click’. So to model the accordion digitally, they need the pressure information as an input. Just like you would measure how fast/hard a pianist was striking the keys to model a piano note on a keyboard synth. I suppose it could have been done with a spring and a strain gauge instead of a bellows and a pressure gauge.