Ask HN: Are there any music composition programs for Linux beginners?

I'd like to enter short melodies and see what a computer could elaborate on. Kind of like computer jazz or something. I'd like to compose songs that are only about a minute and 20 seconds long that I can string together to make a video presentation. Is there anything like that in the world of linux? I don't mind cracking open python code to make it work but I'd like to see what is already off the shelf. Thanks in advance.