Keyboard View Score
This plug-in opens a new window to show a mix of a piano roll and a score, making it easier to visualize keyboard positions in the score, with a mini-keyboard drawn along the score with the pressed keys.
You can download it at:
Instructions to run it:
1.Extract the zip file under your MuseScore plugins folder. (Usually "[program files folder]/MuseScore/plugins"
3.Click "Keyboard View Score" in the Plugins menu.