If you are a music student of any capacity, this app is indespensible. Review music key signatures on the go, no matter what your location. Features over 90 different flash cards, including isolated sharp and flat key signatures, sharp/flat numbers, as well as randomized shuffles. I used to drill music notes whenever I could and it made me a better player and musician. Now I use this app to help me learn more music theory, to make me a more knowledgable musician. I wish you way more than luck on your journey through music.