Not too good...
sorry, but there's no way to get different notes on the guitar or flute, the drums sound the same and there's no way to save you're beats. Also, background music isn't the best idea if you're gonna be composing. It's a good concept, but I feel like you can do more with it. What you might do is record or find recordings of different drum sounds and different notes on the flute and guitar and section your images into individual sprites for the holes and strings. It would give more variety to the music you could actually make.