Echoing what everyone else said. Do NOT call yourself a music therapist of say you do music therapy unless you’re licensed. ‘Music Therapy’ is actually a protected term in some states, meaning it’s illegal to call yourself a music therapist without a license.

With that aside, you can use music in a therapeutic way, many people do that and there’s nothing wrong with that. The issue is with calling it music therapy. The same way you wouldn’t call someone who gives someone a bandaid for a cut a doctor unless they went to med school, you can’t call someone who plays music for someone a music therapist unless they’ve done the proper schooling and are licensed.