Sadly, the cat is out of the bag. From your description, it is likely the CO thought you were paying him for the recording session and thus unauthorized work. But if you have previously done work together in the US, and you have paid him - he has worked without authorization.
What is the wait time for a B visa interview in S. Africa? I know for many countries that it is tremendously long wait.
To answer your question - I was denied entry twice to the US and then admitted as a tourist. But what has changed since the last interview?
Good luck