The Circle of Fifths Guide is a multimedia application designed for iPhone users, focusing on music theory education. This free app features an interactive approach to mastering the Circle of Fifths, utilizing engaging mnemonics and visual aids that simplify the learning process. Users can progress through 11 intuitive steps, navigating at their own pace while reinforcing their understanding of sharp and flat keys with memorable phrases.

In addition to the main feature, the app provides tools for exploring key signatures and chord relationships. Users can select any key from the interactive diagram to view its major and minor scales, while the 'Chords in Key' feature allows for effortless exploration of chords associated with each key. The app also includes a 'Chord Shapes' feature that visually displays chord shapes on a virtual keyboard, making it suitable for musicians of all levels.