Ate a lot cpu (in comparison).
The knobs are weird. Usually... drag down=ccw and drag up=cw.
Yeah, I just did some measurements and noticed that if the sequencer canvas is not drawn, the CPU usage is 0% according to my task manager... Otherwise it's ~11%. Something is definitely not right...
Edit: about the knobs, the method I used for rotation (calculating the angle) is also pretty common, at least in VSTi software synthesizers. The advantage in my method is that it offers more accuracy (when the mouse pointer is pulled further from the knob). I originally wrote the knob class for a soft synth of mine, where extra accuracy really matters.