Hello,
Please correct me if I understood your service correctly.
Your website will be hosting a stream (most possibly in audioOnly format).
If you have your data as .mp4, then EMS can serve as a host for your files (by storing these files in the media storage folder of EMS). After this, EMS will use pullStream to itself using the audioOnly parameter, then this will allow itself to broadcast to the players of your users by doing the usual playback for a pulled stream.
This way, your users will just be able to hear the audio you broadcast via EMS -> player communication, and not be able to save anything because EMS will not send your files to its clients.