Though it does not say so in the text, BlueGriffon Editor is available for Linux, MacOS and Microsoft Windows.
Synaptic Software Manager
Synaptic is not installed by default on recent versions of Ubuntu-based distributions. To install it, you must use either the Ubuntu Software Center or the method described here.
Playing MIDI(*.mid/*.midi) FIles in Web Browser
To play *.mid/*.midi music embedded into Web pages while using Mozilla Firefox on an Ubuntu Linux-based system, follow the one step directions listed here.