Updated review: Yesterday I removed the broken app, and today downloaded it again. This time it installed, then worked flawlessly. The info is gold for beginners as well as advanced vocalists, and I do recommend the CVT book as well. When it didn't work, I was worried that I had wasted my money, but today with the new install, it turned out to be a very good buy.
Train to Sing in Tune – Vocal Exercise, Warm-Up, Ear Training and Singing Lesson