Re: Bends: physics and physical

[Pierre <slavio@xxxxxxxxxxxx>]

I posted this and forgot to in include harp-l in the to list.

Pat, sorry for accidently singling you out to answer this. The anwser is
much appreciated though.


- ----- Original Message ----- 
From: "Pat Missin" <pat@xxxxxxxxxxxxx>
To: "Pierre" <slavio@xxxxxxxxxxxx>
Sent: Friday, May 14, 2004 11:02 AM
Subject: Re: Bends: physics and physical


On Thu, 13 May 2004 20:48:44 -0400, you wrote:

>
>Can I get an executive summary please :-)

OK.

Bends are due to the player altering the resonant frequency of the
vocal tract.

The typical blues harp bends rely on the interaction of the two reeds
in a chamber.

The higher note in each channel can be bent to a pitch slightly above
that of the lower note in the same channel.

At the furthest extent of the bend, the note is being produced almost
entirely by the low pitched reed operating "backwards" (ie, in a full
draw bend, it is the blow reed which is mostly contributing to the
tone and vice versa).

Overblows and overdraws work very similarly to "normal" bends. During
an overblow, the blow reed in that channel is mostly inoperative and
it is the draw reeds that contributes mostly to the note, sounding at
a pitch a little above its "normal" one. This pitch can be bent
upwards.

The lower note in each channel can also be bent, but only by a very
small amount before the reed stalls and the overblow or overdraw kicks
in. Valving the opposite reed to prevent the usual interaction means
that these notes can be bent further, but these bends are different
from the previously described bends which involve both reeds working
as a pair.

Erm, I think that's about it!

 -- Pat.