I'm writing a software synthesizer (a VST instrument plugin). I've been working solely on the DSP (audio processing) code for a while, and am shifting gears to work on the user interface.

The synthesis algorithm, roughly, is that the graph on top describes a Lissajous curve which is used to shape the phase of a cosine oscillator, and there are two cycles of said oscillator displayed underneath the curve. The knobs underneath it are the parameters for adjusting the curve shape.

The UI is all OpenGL 3.2 using a convenience toolkit I rolled myself (for layouts, event dispatching, etc). Currently working on hooking the UI into the DSP side of things.