chavisory said: Same as with assistive equipment and service animals-you shouldn’t even touch somebody else’s instrument without asking, usually. Again, unless some kind of unusual familiarity or intimacy creates an exception
Yes. And also, this is *especially* the case if they are not present. Because some instruments are easy to break accidentally in ways that aren’t obvious. If you touch someone’s instrument when they’re not there, they can’t stop you from doing things that will break it.
I work backstage at a pretty big music festival, and one of my jobs is helping the bands set up. It’s my job to carry things for them, but I still DO NOT touch anyone’s instrument without asking them first, and that’s the first thing we teach people who are working with us for the first time. For many people, it’s as much of a boundary violation as touching their body without permission.