You can use your favorite Internet browser to search for and download song files from the Internet. If you have associated the compatible filetypes with Composer, then as soon as the download of the file has completed, Composer will automatically start up and open the file. You will see the MIDI or Karaoke file transcribed to sheet music, or the MusicXML file opened and converted to an editable file in Composer.

Also, you can use your favorite Internet browser to download song files to a folder on your system. Then you can use Composer's File Open command to open any of the compatible downloaded song files.