Following the discussion on the Windlist regarding the possibility of slow vibrato (i.e. less than 2 hz) on the EWI, I tried recording the MIDI output using both the bite sensor and as an alternative the thumb plate. I think that the latter method has possibilities, with a little practice. It is subject to the limitiation however that the vibrato can be on only one side of true pitch (either flat or sharp, depending on whether you use the upper or lower thumb plate.)

All these examples were recorded at 80mm. The vertical green-blue lines are quarter note divisions. Each image shows one complete bar of 4/4 time.

BTW, There is no graph for 4 per-beat thumb becuase I couldn't actually shake my wrist that fast!