What are you trying to hide? “Violin I” or “2. Gloria”?
If it’s the instrument name you’re trying to hide, you’re out of luck - there’s no automatic option with which to do so, though of course you could delete it manually or bring in a custom page template for this page (and similar pages).
If it’s “2. Gloria” that you don’t want, use the “Show Flow Headings: Never” option, towards the top of your screenshot.
I’m sorry. You’re right. That will be why it hasn’t hidden.
But, as you’ve guessed, it’s the player name running header that I want to hide above flow titles.
I see that Leo says there is no way to hide it. Pity. I’ll do it manually.
You can either delete the text frame in the Page Template (so it changes in all layouts which use that template), or delete the text frame on that page directly (causing an override on that particular page itself).