I love the way that you broke theories down into easy to understand discussions and then provided three levels of practice. The practice sessions were extremely helpful in illustrating patterns.
Two recommendations: after completing a section, it would be helpful to have a NEXT button appear that will take the user directly to the next subject. It would also be helpful to have a reminder on the main screen indicating where the student left off.
In spite of these two recommendations I will give you five stars.
piano.don about Music Theory by Musicopoulos, v2.6.1