Looks like if you change the extension of the mp3 to .pdf (.txt didn't work), it can be uploaded to this forum, but it has to be changed back to mp3 by the end user for it to play (or the .pdf executed with software that knows it's an mp3); however, provided it is executed with the correct software it will play. Of course, you're still limited by the 1 MB upload limit, which will limit the usefulness of this feature...unless you break it apart into several mp3's under a meg and have the end user concatenate them together.
Whether or not this workaround is acceptable to the forum admins, well, I'll leave that to Fr. Anastasios to say; but I'm guessing he doesn't want his bandwidth used this way, to say nothing of copyright issues.
(On a side note, it's pretty hard to find open source mp3's...and even when I found them, couldn't find any under a megabyte, had to edit the file to make it small enough to play with...but if anyone's asking the file is open source from http://www.opensourcemusic.com/
...don't want to get anyone in trouble).