Music Scale Trainer is a handy scale and ear training app designed for beginning, intermediate and advanced music students alike. The lite version of this app features all 30 major and minor key signatures, and a quiz mode for them as well, so you can practice your key signature sight reading. The full version puts a wide variety of scales at your fingertips, from modern modes and popular jazz scales to classical north Indian thaats and the Messiaen modes of limited transposition. With both a practice and quiz mode you can listen to and visualize each scale, and then test your knowledge. There's even hints to help you out when you get stuck!