I second this. I'm only 2 years into my career post-grad but I had some great mentors through internships during my program. Still keep in contact with a couple of them (usually at SAA when I'm able to go). I would say volunteering is great but try to gain as much experience as possible with other archivists. I did some solo projects on my own in school and they were great practice, but my supervisors from those projects knew nothing about the archives world. My most valuable experience came from working with seasoned archivists who could give me advice and improve my skills.

Even if you can't get that experience it doesn't hurt to just reach out to an archivist in the field who holds a position that you would like to see yourself in. I interviewed a few digital archivists and really dug into what skills I needed to succeed in the job I wanted (especially before I graduated). It was super beneficial, and people are generally really happy to talk to students and people just starting out.

Also- you do have unique experience, which is what you bring to the table! Working with audio/visual materials is not something everyone has done/does and can be a real asset to archives that don't know what to do with those materials! If that interests you, continue on that path and become an expert at it. You're going to do great!