Ericsson Melody Player is a free and useful application.
Happy owner of a GF768, I spend some time looking for melodies on the Internet, but I found very anoying to enter the melodies in the phone to see how they sound. So I decided to make a player, and here it is, use it, it's freeware. It handles melodies in the same format as the phone (bemol are not handled, use # instead).
There is 2 ways to use Ericsson Melodie Player:
If the player is not associated with .em files or if you want to play melodies from other sites, just select the melodie itself (highlight it with the mouse), then copy the selected text in the clipboard (Edit Menu -> Copy) (Ctrl-C) and then click the 'play clipboard' button of the player.
Type in your melodie and click the 'play' button.