This is a controller and synthesizer app that I designed during grad school for an iOS audio-app writing class. The playing side, on the right, can be thought of as a single octave of a keyboard wrapped around into itself. The yellow keys would be the white keys, and the blue keys the black keys. The root note of the chosen key (selected in the top left corner) is always mapped to the 9-o’clock position (where C would be on a piano). By choosing the desired scale degree from the vertical selector on the left, the respective degree’s chordal tones “grow” longer towards the center of the circle. In this way, the user has 3 concentric circles of playable notes: the innermost being the chordal tones, the middle being the scale tones, and the outer being the chromatic tones. As the user passes the root note of the selected degree in a clockwise or counterclockwise direction, the octave is automatically incremented or decremented, respectively. The monophonic, two-oscillator synth engine is written using the Audio Units API and contains some fun controls such as a visual wave-shaper (create and drag way-points on the input-output transfer function line) and multipurpose track pads.