Major update! Modernized with Kotlin and Android SDK 36. All libraries updated to latest versions — Firebase, Material Design, AndroidX. Improved performance, stability and security. Make chords with numbers. Pick a tone from the orange circle at position 1 of the green circle. Tones 1-3-5 form a major chord, 1-b3-5 a minor chord, 1-3-5-7 a major seventh. Every chord uses the same numbers for all tones. Circle of fifths included. For smartphone and tablet.