Select your song file in the Finder and Zip it from Finder/File/Create Archive.

Create a text and/or image link to this file in the  “Link” inspector by selecting  “Link to: A file” and selecting the file in the “choose” popup window.

This link will not work in iWeb but, when clicked on in the published site, will download the file to the viewers desktop.

Download the The Drunken Scotsman by clicking on the tartan icon.