[Harp-L] Re: Altered reed shapes

[Rick Epping <rickepping@xxxxxxxxx>]

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> The spectrographs of all the harmonica reeds I studied while conducting
research for Hohner showed what appears to be a low signal to noise ratio;
that is, the amplitude of the dissonant overtones was very low compared to
that of the consonant overtones.  The amplitude of the dissonant overtones
only increased significantly when the harmonica reed was blown loud enough
to start distorting.  I believe that what makes harmonica reeds sound thin
and reedy is the relatively high amplitude of the upper partials, or
consonant overtones, and not so much that of the dissonant overtones.



Some aspects of reed design that can influence the strength of the upper
partials compared to the 1st partial, or fundamental tone, are: 1. Reed
thickness (especially the thickness of the reed at its edge) - a thin reed
will have stronger upper partials than a thick reed.  2. Reed dimensions - a
narrow reed will have stronger upper partials than a wide reed.  3. Reed
plate thickness - a thin reed plate will produce stronger upper partials
than a thick reed plate.  English-made concertina reed shoes are undercut to
create the effect of a thin reed plate, giving these instruments their
characteristic reedy tone.



I believe that what is at least as influential as the reed to the tone of an
instrument is that of the instrument design and construction.  For example,
clarinet accordion reeds in cassotto are identical to those in the same
instrument that are not in cassotto, yet the tone of cassotto reeds is
significantly warmer and rounder than those not in cassotto.  This is
because the cassotto tone chamber shifts energy from the upper partials to
the fundamental, making the fundamental actually louder than that of the
same reed not in cassotto.  While playing a harmonica note into a microphone
to produce spectrograph, I found that going from an uncupped note to a
cupped note caused the amplitude of the upper partials to decrease and that
of the fundamental partial to increase, just like an accordion's tone
chamber.  Similarly, the reeds of an XB-40 are identical to those of a
chromatic yet, due mainly to the XB-40's internal valve chamber, the XB-40
produces more of the fundamental tone and less of the upper partials than a
chromatic, giving it a warmer, rounder and loud, but less bright tone.



Italian accordions might be characterized as having a warm, pure and round
tone compared to German accordions, which tend to be more bright.  Here are
some possible reasons: 1. Italian reeds tend to be thicker and stiffer than
German reeds (this need not affect response, as stiff reeds can be given
less offset than more flexible reeds).  2. Italian cabinets are generally
thicker and heavier than German cabinets, and can absorb more of the upper
partials.  Likewise, Italian reed blocks may be heavier than German reed
blocks, having the same effect.  3. Italian accordions more often use
leather reed valves and German accordions usually use PVC reed valves.  The
heavier, softer, rough-surfaced leather valves absorb more upper partials
than the thin, reflective PVC valves.  Lastly, 2-voice tremolo tuning on
German accordions is usually faster than the standard 2-voice, Violin tuning
common to Italian accordions.  This also helps to give German accordions a
brighter tone compared to the more pure tone of Italian accordions.



Some harmonicas can be overly bright, especially harmonicas that have been
customized for maximum performance.  But in general, most players might
prefer a somewhat bright instrument, where there is a greater possible range
of tonality by means of hand cupping.  A bright harmonica can be made warmer
and more fundamental in tone by means of cupping, but less can be done while
playing to make a harmonica with a predominantly mid-range tone more bright
sounding.



Rick

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>
> Message: 5
> Date: Wed, 11 Aug 2010 09:59:27 +0100
> From: "Dr. Michael J. Marino, DC" <m.marino@xxxxxxxxxxxxxxxxxxxxx>
> Subject: [Harp-L] RE: Altered reed shapes
> To: harp-l@xxxxxxxxxx
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> Good points and thoughts folks,
>
> Now I need to point out a few points though.
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> Most Accordion reeds in the range of the harmonica are single rivet
> reeds (I just double checked some I have in the shop for making
> concertinas), these are Voci Armoniche, typo a mano and Cagnoni typo a
> mano reed sets.  Only the lower reeds I can not sound with my
> mouth.  The Air button on an accordion or a concertina serves a
> couple of different purposes.  They range from filling or emptying
> the bellows for a diatonic type of instrument so the desired reed can
> be played.  With chromatic instruments the ability to close or open
> the instrument with out sounding a note.  Opening bellows without
> either a note depressed or the air valve open damages the valve covers
> (pallets/spoons depending on instrument), the bellows, and any
> gaskets/seals on the instrument.  As air will get in or out depending
> on direction of force.  Though I don't see the mechanics for damage
> to the reeds via the avenue.
>
> That set aside, as it is not really the subject of interest, my
> interest is in finding a "cleaner" sounding reed. By cleaner I mean a
> tone response that is sharp and clear in the desired note and lacking
> as much as possible unwanted secondary enharmonic tones. There are
> desired tones and it is interesting that the reed form used on
> accordion reeds seems to re-enforce those as well. Both Hohner ans
> Seydel have shown that steel reeds can be produced that will respond
> to the amount of force that a person can produce to cause a reed to
> sound. What i am looking at is how to bring a bit more of a clean
> exact sound to the reed.
>
> I know that not everyone will consider this a good thing. My interest
> is first finding out what the reed shape would most likely be that
> would work and than letting folks see if it is a pleasing sound. I am
> doing this as a personal research while not working on clients
> instruments, so I can take my time and try a few different option to
> see what is best.
>
> So to all thanks for what input you have already given and please
> feel free to discuss further it makes me think and look at options in
> the design structure to work toward an optimum.
>
> Michael
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