I realize this feedback is too late but I just wanted to say well done! It's an awesome piece of work and I hope I can afford it.
But, anyhow, great job. I especially like the clear photos of the instruments and the animation of someone playing them, along with the instrument's actual sound. So much better than the music flashcards I show my son.
I think everything else you have is great and I love the VERY many different ways you approach the same thing. The color scheme for some of it (that red with that green) does look a little ugly to me - I'm not sure if such shades are used for a purpose I'm not aware of.
On a different matter I was thinking it would be awesome if you could come up with an "everything" program - reading, math, music and science (chemistry, physics, biology), mabye others (art anyone, color schemes and mixes etc). I've noticed that it seems more 'fun' when it's all mixed up instead of doing numbers repetitively. Also, if you mix music with it all (especially if you utilize the right brain learning relaxation music) it would make it even better. Also, I would like to see the use of more color as that helps memory. Last but not least some positive affirmations wouldn't go astray either.
In summary, great job, I just hope I can afford it!
PS. Others have mentioned too - I definitely would put something on the blank music page - maybe a synthesizer-type version of the music such as you can find on YouTube where you see the notes descending the screen before they hit the piano or maybe a high quality video of an orchestra performing the piece?