There are too few details here and your question is too vague. But I would say that the question is not “can they legally?”, but rather “will they?”. If they c

There are too few details here and your question is too vague. But I would say that the question is not “can they legally?”, but rather “will they?”. If they claim ownership of your music, and threaten to sue you for it, you’ll probably just give it away, cause paying a lawyer to defend your right and enter a lengthy court battle is not going to be worth it. Now your employer has nothing to do with music, and sueing an employee over bogus cooyright claims doesn’t look too good on glassdoor. So there’s zero interest for your company to claim ownership of your open source music… Personally if I were you, I wouldn’t be too worried.