While not an officially supported feature of Shivtr, you can add music to your site by embedding a web audio player in your site such as www.podsnack.com.
To do this, simply sign up to PodSnack and create your playlist, then when you are finished click "Publish". Then in the "My Playlists" page, click on the "Embed Code" option and copy that HTML.
Then, login to your Shivtr Site Admin and go to the Layout tab and add an HTML block to your site, and paste in that HTML, and you're done! =)