There may have been recent changes to the certificates required, but musicians have always been treated with suspicion by immigration authorities.
Some years ago my partner was a professional musician who worked regularly in the US. Consequently, there were lots of American work permits in my partner's passport, so even if we visited America for personal, non-work reasons we were always questioned at length before being admitted into the US.

Canada in particular has always been stringent in its treatment of foreign musicians, so it's ironic that a Canadian musician fell foul of our regulations.

I think that countries assume that once you've worked there, your return visits are less likely to be purely personal.