Thank you Lloyd but no... I do not suggest by any means that a square wave or complete closure is the only contact mode. On the contrary it seems essential that other effective contact formations would occur. The trapezoidal form for example has all the harmonics. My interest in the square wave in particular is in the relatively large energy content in the early odd harmonics. A square wave shape is extremely advantageous if excitation of one or more resonant cavities is the primary goal.
I'd be interested to know if in the observation of the tract you were in a position to observe altering patterns of cord contact and the related harmonic content.
Referring once again to the square wave form of contact of the cords... it is not essential that the contact formation be perfect. A slight rounding of the contact corners, that is a slowing of the rate of contact and release, would only reduce the upper odd harmonics without being at all detrimental to the 3rd or 5th. The forever intriguing part for me is that the "pressure wave" and "rate of flow" wave, the two component parts of energy, are 90 degrees displaced one from the other. Such a relationship is a classic flywheel, potential energy description, yet with a velocity altering from pitch to pitch.
Reg.
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