Yes an iframe is HTML and can be inserted into another HTML page.
But it has nothing to do with Flash and cannot be used inside a .fla as part of a Flash application.
There is very little you can do to modify an iframe and I don't see how it would fit into your original project.
But yes, you can use that iframe on an HTML page. Just remember that you are not accessing the actual .mp3 file but rather loading a separate HTML page into an iframe which is then embedded into your own Web page.
Best wishes,
Video Man