At the shell prompt in the developer setup....

mount -n -o remount,rw /drive0
mv /drive1/fids/100 /drive0/fids/100
mv /drive1/fids/101 /drive0/fids/101
mv /drive1/fids/110 /drive0/fids/110
mv /drive1/fids/111 /drive0/fids/111
mount -n -o remount,ro /drive0


The 1st mount command allows you to read-write to the first disk's music partition, the 2nd mount command sets it back to being read-only.
The mv (move) commands moves the files from the 2nd disk to the first.

David