All you have to do is sing. We'll take care of the harmony.
Harmonify is a software program that takes input from your microphone, figures out what note you're singing, and then generates harmony notes for the note you're singing. So far, we just do the fifth of the note. Later, we want to have a system driven by a well-trained ANN (artificial neural network) that can modify the type of harmony based on what it thinks should come next. We'll see.