I would have to say as well the closest blog you'll get to those requirements is Blogger or a personal webspace of your own.

For the audioclips, I think you'll need to find another way to host them on Blogger later because they don't have such a feature as of yet.

In terms of customizable blog features, I assume you want to customize the design and layout a little. Well, Blogger can do that though I think now they're more strict of using XHTML.