Master the Circle of Fifths so you can improvise with confidence and recognize chord relationships instantly. Practice in short, focused sessions with an intuitive flashcard system featuring 3 levels of difficulty … Basic Mode: Learn where every key sits on the Circle of Fifths (dominants, subdominants, and relative keys) Advanced Mode: Identify chords by scale degree using Roman numerals (I–ii–iii–IV–V–vi–vii°) Expert Mode: Learn to create interesting chord progressions using - Secondary dominants - Borrowed chords - ii–V progressions - Tritone substitutions - Diminished chords - V alternatives Earn stars as you improve, stay motivated with a clear sense of progress, and review detailed statistics to see how far you’ve come. When you want a real test, turn on Hard Mode for a tougher challenge. Featuring English and German notation (In German notation, B is written as H, and Bb as B.) No in-app purchases or microtransactions! It's never been so easy to build chord fluency :)