[Harp-L] very simple questions

[Zombor Kovacs <zrkovacs@xxxxxxxxx>]

I have 2 very simple questions to those interested and
involved in harp physics. I am a mechanical engineer
myself having learnt fluid dinamics and acoustics, so
I will most probably understand a scientific
explanation.

Why can a note on holes 1-6 be bent down drawing the
air? 

Why can a note on holes 1-6 be bent down blowing the
air if the lower reedplate is replaced with a lower
key reedplate (eg. replace C lower reedplate with Bb
lower reedplate)?

I am fully aware, that bending down a note is possible
(almost) as low as the lowest sounding reed in the
hole. What I am asking is, why can I DRAW bend if the
blow reed is lower sounding and why can I BLOW bend if
the blow reed is higher sounding than the draw reed?

In other words, why cant I blow bend UP on eg. hole
number 1 on a standard blues harmonica? All I can do
is "overblow", but not BEND in the same manner as draw
bends work. It must have an aerodinamic, or at least
physical reason. 
Perhaps Mr.Antaki could answer me this question. I
dont know if any research has been done on this topic.
There must be a reason, why bending can only be done
"towards" the lower sounding reed.

thanks
Zombor

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