Structure

[JelMain]

You have a duplicated level in the main forum site, which may perhaps be resolved by renaming it as a generic sublevel.
As an opening bid there, I would suggest main headings as:
Technique
Education centres
Teachers list
Teaching technique
Repertoire list
Choirs list
Events list
Agents list
Accompanists list
Composers list
Other

[thevocalistadmin]

theVocalist Forum and Mailing List is the main forum and the mailing list. There is no duplication there - it is simply one forum with seperate threads. There can be no sub-forums there since that would not work with the email integration.