Your server will receive a request at http://site.com/audio/1234
. Somehow you will need to be able to return some content.
For now the only strategy I know is to render that page on the server-side also... Which involved some (or a lot of) work.
It's also good for the browsers that does not support pushStates yet. That way these users can still access the data.
You can also take a look at this http://docs.meteor.com/#spiderable They render the page on the server-side by executing the client-side javascript on the server-side.
Here's a similar question: pushState and SEO