ok V@no
i got a local solution
i can upload the mmf files to thumbnails directory through FTP.
Now let me explain what i want:
for example i upload a midi file named (myfile.mid) as image.
and upload (myfile.mmf) as thumbnail to thumbnails directory manually (ftp).
now if we access myfile.mid details page there is download and download zip button now i want if we click download let (myfile.mid) to be download and if we click download zip then download(myfile.mmf).