So Posterous says this should be easy. Easier than with Blogger or WordPress or Dreamweaver or Drupal or any other common CMS.
Youtube embeds are easy enough.
Even native video files are probably relatively easy to upload, although having established a YouTube channel, why bother with anything else?
But let’s say I want to embed an MP3. Well, media tab over there says I can upload audio.
So it was just a matter of selecting the wav file. Presumably this will work for an MP3 as well.
Next: figure out how to get into the HTML.