Re: [Harp-L] very simple questions

["Tim Moyer" <wmharps@xxxxxxxxxxxxxxxxxxxx>]

Zombor Kovacs wrote:
> Why can a note on holes 1-6 be bent down drawing the
> air? 

The primary sounding reed is the closing reed of the pair.  So if 
you're blowing, the closing reed is the one mounted inside the 
plate, the "blow reed".  In holes 1-6 of a standard tuned diatonic 
harp, this reed is lower in pitch than the opening reed, the draw 
reed.  When you're drawing, the reed mounted on the outside of the 
plate becomes the closing, primary reed.  

When sounding the higher pitched reed, the lower pitched reed acts 
as an auxiliary reed, vibrating sympathically slightly closer to its 
tuned pitch.  This encourages the primary reed to drop in pitch, 
which can be encouraged by the size and shape of the mouth and vocal 
tract of the player.  If the player creates a resonant cavity that 
encourages this drop it pitch, the auxiliary reed assumes a greater 
and greater role in the production of the apparent pitch.  When you 
approach the limit of the bend the auxiliary reed is acting nearly 
alone in producing the note you hear.  This is one reason that blow 
reeds often fail on holes where players draw very hard to achieve 
deep "bends".

When you get to the upper end of the harp the process operates in 
reverse.  The blow reed is now the higher in pitch of the pair, and 
the draw reed acts as its auxiliary, enabling the production of blow 
bends.  The principle is the same, just the air directions have 
changed.  

> 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. 

The overblow works without an enabler.  With the gaps set properly 
and with the proper technique it is possible in the lower end of the 
harp (1-6) to "choke" the blow note and force the draw reed to 
sound.  Once this reed is isolated it's possible to vary its pitch, 
such that overblows can be bent upwards.  Likewise in the upper end 
of the harp (7-10), it's possible to choke the draw reed and force 
sounding of the blow reed as an isolated overdraw.  

Hope this was intelligible and helpful.

-tim