a suggested implementation of download of music would be:

on the file tag info screen where you have the Location field which is just a link back to the same page. to make that link a link to the file do allow download to the client.

as for Upload, it would require you to enter the artist ablum and title, and allow you to opptionally enter the other tags (year, track number, genre...) and would upload it to a directory inside your music folder, e.g. %musicfolder%\%artist%\%album%\