TuxGuitar for Windows is a great little editor program for musicians. It offers a large variety of options and can read and save files in many different formats depending on how you want to use them. One great feature is that it's an open source program so you can always find unofficial updates from other users who want to improve the program.
Of course you can use the program to create new musical scores or edit those scores. You can also use it to edit MIDI files which have already been designed. Another great feature is that it can both import and export files for Guitar Pro so you can easily trade between various instruments.
Not only can you add regular music notes in you can alter the track, beats, or measures changing how the entire score sounds. Additionally this program has a number of effects built in that can control both different notes and different tracks. Using them in different places and different ways allows you to create a highly customizable musical work. You can select where certain instruments should be played or should be muted. The program will give you a visualization of the track that you've created so you can keep track of everything. You can also select colors to help make this easier.
If you want to come back to your work later you can always save the file to your computer and then reopen it at a later point. If you'd like to use your creation elsewhere you can export it in different file formats that work with various players and programs.
Overall this is a really great program that helps you design your own musical tracks. It helps if you have an understanding of how to read music since it gets rather technical. But even if you don't it's easy to explore and play with the program until you come up with a great sounding song!
This tablature editor lets you create various different file types and edit them in many different ways