It’s easy to just assume that since a live band is simply playing their instruments that no further sound equipment would need to be involved or that they would just automatically bring their own. If you’ve learned anything in life, it’s that you shouldn’t roll the dice and chance that everyone is on the same page with that stuff, or you may end up with neither the venue or the band having the equipment necessary on the day that it counts.
Ask the venue about their sound system and if they have speakers, microphones, extension cords or other audio equipment a band might need. If they’ve ever had a band play their before, they should be pretty familiar with what a band might need, even if you aren’t (after all, you only ever needed to know what your 8th grade Guitar Hero “band” needed in order to play loudly over the tv and annoy your family or friend’s family).