A simpler solution: Use the appropriate shareware, a single download.

Download "Melody assistant" from Myriad. It's shareware, use not limited in time. As mentioned above MUS files are the Melody (and Harmony by the same company) format.

http://www.myriad-online.com/ /en/products/melody.htm

I use Melody all the time - fabulous. Much greater flexibility than Notepad as far as I'm concerned.
I use it with OMER which is a score recognition tool by Myriad. Though OMER I find more difficult to use, requires a fair bit of tuning to recognize scores properly.