From the amount of fairly big gear that was being offered, it appears accordionists were working hard to be heard right at the dawn of the rock 'n' roll era. I'm thinking Wurlitzer, Baldwin, Selmer...they all had big amps aimed at the accordion trade, IIRC.
A load of regional dance music styles in both Europe and the US use the accordion, so I guess accordionists were regularly having to fill large dance halls in the days before decent PA systems, even if they weren't pushing the volume to extremes like the rock n' roll guys. I played for a while with an accordionist who was still into working that way, and it turns out an accordion with a crude internal mic through a 100 watt tube amp is about as brutal in the volume wars as many guitarists I've played with!


