Are There Any Freeware Music Creating Programs?

I'm looking for something that I can start completely from scratch and add different musical instruments or sounds onto a storyboard to make my own tunes. I don't want something that just mixes or alters music from other people or bands. I want to be as original with my music to add to some of my videos. I also don't want to pay for it, I just want to download it if there are any out there.