Hi
One thing and then it is perfect and you can stop development: I don't want the whole USB hard disk scanned for files, but just a subdirectory.
You can drop a file named ".mpdignore" in every folder you want to exclude from indexing.
From
http://www.musicpd.org/doc/user/music_directory_and_database.html
To exclude a file from the update, create a file called .mpdignore in its parent directory. Each line of that file may contain a list of shell wildcards.
for example:
echo "*" > </path/to/directory/to/be/ignored/>.mpdignore
Frank