I'm a musician and have toured Western Europe a couple of times (and know a lot of others who have). Apart from the UK noone I know ever gets working visas, and this is never a problem crossing borders honestly saying to immigration that we're there on tour in a van full of music equipment and merchandise.
There are separate arrangements for touring groups. However, if you're not from the EU then good luck. You'll notice that there are huge complications after brexit. That said, likely nobody will check, care or notice.
Maybe it's a "noone cares" thing, but this includes some American friends who were caught with weed in their tour van at the Norwegian border and still didn't have any visa issues (and somehow still managed to get into the country!)
Even if noone cared, relying on the apathy of others seems like a poor part of a business model. Unfortunately, they do seem to care at the US-Canadian border entering the US. There have been a few Canadian professional wrestlers, like Mike Bailey and Super Smash Bros., who were barred entry to the US entirely for 5 yrs because they were caught trying to work in the US without a visa.
More on the topic of musicians: https://www.huffpost.com/archive/ca/entry/us-border-canadian...
I think this is all silly, of course, especially because American acts have seemingly no trouble working in Canada. I shouldn't take for granted when I saw the Canadian band badbadnotgood in the US last month...
Yes, but that is a case where they're getting paid in the US to work.
The one conference horror story I recall from a few years back was someone was going to speak at some small UK(?) conference and they were getting an honorarium or something like that. And they told immigration and I think were denied entry for that reason. But I've spoken at dozens of events for free and it's never been an issue.