ofxTonic
This is a wrapper for the Tonic Audio library. This library provides a simple interface for efficient audio synthesis. You can generate and combine various types of waves (sine, triangle, square, etc) and add effects to them. This looks like a great go to library for any basic audio synthesis needs.
ofxUI
This is a great UI library which provides a lot of good default widgets with a nice look. I can see myself using this library for any UI I need in openFrameworks.
ofxKinect
Having good Kinect integration is key when you want to combine skeleton tracking with audio synthesis…
Good finds — curious if you could write (speculate) about how you might use these together? Or why they interested you in particular?