The app’s main function is to tell you if you’re in tune. But it doesn’t just tell you--it shows you. Play a note, and you’ll see your pitch traced as a vertical line on the screen. If you’re within the green band in the center, you’re money. If you’re to the right or the left, you’re either sharp or flat. But what’s so great is that the feedback isn’t limited to that instant. The app continually charts the last second or two of activity on your screen, a "pitch history" that gives you a simple visual sense of how steady you’re playing.
Recently I was having lunch with friends that are music teachers and performers. Ella Fitzgerald started playing in the background and we were discussing her amazing voice when one of my friends remarked how she had perfect pitch, which is why she could so easily scat the way she did. The idea of perfect pitch is fascinating and mind-boggling to me. Almost immediately after that conversation I saw this app and I could not help but think that while most everyone needs this app to help them all that this app accomplishes was happening in Fitzgerald's mind in real time while she performed. She didn't need an external reference, she had this app in her head.