Wow.
That was awesome. That must have taken a lot of time and skill to make.
I just have a couple suggestions.
I could not figure out how to put two different sounds on the exact same note. Some people might want to use that, like having two guitars on the same note.
Also, it seems that the sounds can only be placed on each beat, not in between beats.
Last, I think it needs a bass clef as well as a treble clef.
Other than that, it is freaking awesome. Good job!