Dance gardens. Massif Central had a thriving dance tradition... bagpipes were common, called "musette." Accordion thrived in Germany, and France and Italy both developed local manufacturers. After World War I, migrations brought many dance cultures together. Accordion let one person line out both rhythm & melody... economic advantage.

There used to be good webpages, but searching now, it all seems like store results... "bal musette," "tony murena", "gus viseur" are some starting searchpoints.