Since email uses this and it doesn't look like anyone else is likely to have much knowledge of this module, I'm going to assign it to myself so I don't forget about it.

This module has no unit tests.  It would be really great if you could create some to at least test for this regression.  I'll be glad to provide guidance on the test suite if you need it, but I don't know all that much about audio files so I'm not in a position to write the tests myself at the moment.

The first changeset is just the translation to bytes, I don't see any issues there.  I'm adding Victor as nosy since he wrote the second changeset, but the fix looks straightforwardly correct to me.

By the way, if you had written r56957 and r56987, roundup would have turned them into links, instead of quoting the link you did supply so that it wasn't usable :)