Currently Being ModeratedJan 18, 2013 7:51 PM (in response to t0pgun)
Anyone with access to your site and server should be able to post a audio file (mp3). It's just a matter of uploading the file and posting a link.
If for some reason this isn't possible you could use a blog site like wordpress that will let anyone with the password upload and post audio. You could simply link to the blog site from the main site. The poster could upload the file to a post, add a title and even write a short description.