There are many ways to demonstrate interest beyond an in person visit. Your S can do virtual sessions, sign up for emails and open/click on links in them, reach out to the AO with a question for which the answer is not readily available on the website, or meet with the rep during their in school visit.
For the music trial lesson, your S could reach out to the AO to get recommendations for who to meet with, and then follow up with them after your S has that session.