Keep in mind you can be base bound or mobile when sending the audio file.
My suggestions below. Your comments welcomed.
Authentication (not really metadata)
Username
Password
Domain
Content information
Channel
Category
Title
Description
GUID - optional - if left blank server creates one, if one supplied system uses that GUID -if GUID already exists writes all metadata in place of existing
Date/Time: Time media created
Language
Media type information
Stream type: fixed file or streaming
Content type: mime/type - mandatory
Rules of all multipart MIME data streams as outlined in [RFC 2046]
Blogging Style information
Moblogging or baseblogging
10-20, location, state information: home, on the road, on vacation
Device type: PDA, notebook, cellphone, desktop
Social information
Enable comments - optional, enabled if not present.
Enable media type comments -