FractMus is an old windows application. In order to work in Windows 10 you need to first install the following (freeware) applications:
CoolSoft Midi Mapper
CoolSoft Virtual Midi Synth
A general-purpose Soundfont Library for CoolSoft Virtual Midi Synth
If you are a Mac user you'll need to install it on a Virtual Machine running Windows. I recommend VirtualBox.
Here you can watch tutorial on how to install Windows XP in VirtualBox
Download FractMus installer here
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