Q: I came up with a nice melody I really like and I can play it with one hand on the piano, but how do I figure out how to accompany it with both hands?
A: try playing it at parties. play it at 10 parties and after the 10th party you'll find something. it might be with your voice. it might be someone else doing it. it might even just be in how you frame the melody in context, based on what you say to people before or after. as soon as you start using this thing for communication, then you'll start seeing what it can do