"...the folds will tighten to produce the pressure even though the resultant sound will not be very full for lack of air. The tightening could cause a loss of both extreme high and extreme low."
Would this produce a sort of whiny or edgy sound? Listening to myself in recordings (I tape all my lessons and often my practice time), I always feel that my voice doesn't have enough resonance and always has this 'edge' to it which I find unpleasant to hear.
If tightening is the problem, how do I solve this?