So you know you want a career in music and you keep hearing how important internships are, but you're still not exactly sure what you should do with that information?
The real answer to the question of when you should do an internship is as soon as possible. Preferably, you should start getting some music industry experience as soon as you realize you want to work in the music industry. Practically speaking though, this is not always possible. This brings us to the second point.
Most internship programs require you to get college credit in exchange for your work at the company. This means you obviously need to be a college student and that you also need a school that either requires internships or co-ops or will at least allow you to pursue one in exchange for course credit. So you should take full advantage of your time in college by doing as many internships as you possibly can. Don't just wait until your junior or senior year to begin pursuing internships. The sooner you start, the more time you have to lear, get experience, build connections, and establish a good reputation and these things are precisely what an internship is about.
Outside the Norm
You can of course find some other opportunities to do internships even when you're not a college student. Some smallers companies don't have this college credit requirement and can be a good place to go when you're looking for experience but aren't a student. Volunteering at music related non-profits can be another good way to get experience without needing to be a college student.
Thanks to Tallen for inspiring this one.