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From: "Mike Will"
Date: Wed, 14 Jan 1998 09:18:44 PST
Subject: Re: Held Bends [A `bit' long!]

>From: Bobbie Giordano

>I have to disagree
>with numerous accepted notions that ~certain~ mouth positions are even
>necessary to produce bent notes in the first place.

I have found that there is more than one way of getting many (especially
draw) bends.. so I agree that mouth position is not a necessary factor
in every bend.

Bends can be done by constricting the airflow by:
- - pinching the lips (generally not a good way to get bends, but can be
useful on the 3' (3 draw half step bend)
- - humping the tongue (gross as that sounds..)
- - tightening the throat

>The shape of the various parts of
>the vocal tract can surely affect the notes' resonance, loudness and
>intensity by interacting with soundwave factors such as superposition
and
>constructive or destructive interference of the soundwaves, reflection,
>absorption and harmonic overtones. These are elements of fashioning
the
>resonant cavity in which the notes sound their best...hopefully! But
they
>do not, IMO, "cause" the reeds to gyrate and speak.

They may also set up an environment in which *it is easier* for a reed
to vibrate at *one* of it's characteristic frequencies for a given
airflow, because of the resonance characteristics. Physical systems
tend to do what is "easier", so in some sense the environment is aiding
in the causation of the reeds selection of vibrational frequency.

>In a dual reed system, there is another reed sharing the chamber
>with the reed that may also be so induced to vibrate at the same time.

However, in the Discrete Comb dual reed system, the reeds *do not* share
a chamber. They do not share turbulances, or airflow direction.

*** Yet, 2 reed bends work as normal! ***

Continuous 2 reed pitch change bends occur, AND THE 2 REEDS SYNC TO THE
SAME PITCH! Since the chambers are separate, the only mechanism that
can couple the two reeds together in pitch is in the players body, not
in the harp.

As far as I can figure, the resonance in the players body is the only
factor that can couple the 2 reeds together to vibrate at the same
frequency, despite the fact that they have different "natural"
vibrational frequencies due to their length.

>One thing we all do to bend
>a note is constrict some part of our vocal tract, whether for a blow
bend or
>draw bend.

Above I described some constriction mechanisms. BUT, it I believe it is
possible to get good deep bends without constricting part of the vocal
tract.

These bends are often described as "from the diaphram", "resonant
bends", or bends with "an open throat". Magic Dave has described
"effortless" bending from below the throat. The MRI that Garry Green
made shows the throat *opening* at (what I believe is) the point of the
bend.

So I don't think that constrictions are required.

>My point is that the constrictions we use to initiate bends are
altering the
>air flow which alters the note. As you constrict the vocal tract
somewhere,
>you cause the air to speed up to maintain the same driving force of the
air
>flow. This also results in the Venturi effect, which means that as the
>speed of a fluid [or air flow] increases the pressure drops in the area
of
>constriction, but, also, as you increase the velocity of the air flow,
even
>ever so slightly that you may not even notice it, the pressure in the
vocal
>tract drops in general.

During a draw, the lungs create a pressure drop that forces air in
through the harp, through the mouth, throat, etc and into the lungs.
Pressure differences in the harp, mouth, and lungs are due to
constrictions at the lips, tongue, and throat. Opening the throat
decreases the constriction and tends to equalize the pressure in the
mouth and lungs. The lowest pressure is in the lungs, since they are
"pulling" the air in (air flows from high to low pressure). So, the
pressure drop hypothesis is not discounted because of "open throat"
non-constriction bends.

However, I am still puzzled as to why the "overbend" associated with a 2
reed bend is not achievable under the same resonance/pressure conditions
when shifting from normal play to single cell play on a discrete comb.
Somehow, the other reed in its own separate cell is back influencing the
ease of the overbend in the other cell..

Mic'l

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