You really don’t have to worry about it. In Canada venues are required to have a licence to have music played (SOCAN), and that extends to anyone performing in the venue. If they don’t have it, it is on them, not you.
When I was still playing off of CD’s, my general rule of thumb was to have a legitimate copy of any song that I may also have a remix of. In the event anyone gave me a hard time, I could pull out the original disc from a CD pool and it would be covered off. With most people having gone digital, it makes it even more grey. Until changes to copyright laws actually get passed and court tested, as long as you aren’t selling your mixes for profit, it is doubtful anyone is going to bother you.
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