Because it is volunteering for a few days, not actual work. And less than a week. It is in Canadian organization. Similar to case when your friend from Canada has a wedding and you go sing there for a few days for fun so not for paid thing. There are other people who are Canadian citizens there too doing the same thing for volunteering and for fun and none gets paid . Although singers are considered to be paid work, in this case it is not because it is done for fun and volunteer and others do it from same reason too. Some still mentioned work permit for this and i find it hard to believe and out of any logic.
