Hey @jonah! Can you test on the streamlit-nightly? You can install it by uninstalling streamlit and run pip install streamlit-nightly.
To explain the problem, Safari requires the server to support Range Requests. We found this problem with regard to videos, so I am sure this would also apply to audio
See https://github.com/streamlit/streamlit/issues/1804#issuecomment-687328551
If it works great, it will be included in the next release.