Hi
apologies if I've broken inter forum etiquette.
I play harmonica and since discovering melodeons the following suddenly has more relevance its an extract from a news group called Harp-L this is Digest Vol 84, Issue 33 in part ... a conversation about how different reed block constructions affect the tone with regard to harmonicas but is based on theories from accordions........
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I'm sure there are sites dedicated to accordions- didn't Winslow mention an
accordion forum? Concertina.net has some good concertina related
information.
A reed block is the part of an accordion that's like a harmonica: a wooden
battery or comb onto which the reed plates are attached. A reed block is
mounted onto the inside of either the treble or bass foundation plate. The
key pallets (valves, or Klappen (German)) rest on the opposite, outside of
the foundation plates and are raised by the accordion's keys or buttons,
allowing air to pass through the reeds, either into or out of the accordion.
The foundation plates are part of the bass and treble cabinets, which are
the housings on either side of the bellows which contain the reed blocks and
key mechanisms.
Cassotto, or tone chamber accordions have one or more sets of reeds for
which the reed block is not set onto a foundation plate but onto a box about
the same size as the reed block, with one internal chamber shared by all the
reeds. This tone chamber is set onto the inside of the foundation plate,
which has one large opening to the outside, into which the pallets are set.
If a reed block is the equivalent of a harmonica, a tone chamber is the
equivalent of the harmonica player's cupped hands. Tone chamber accordions
are relatively expensive, partly because of the extra parts needed, but
mostly because it is very labor-intensive to adjust the key mechanisms of
tone chamber accordions.
"Reed shoe" is a term used to describe the individual reed plates in
English-made concertinas. They're called reed shoes because they are
somewhat shoe-shaped, tapered so that they can be wedged into the wooden
reed pans (the concertina's equivalent of a reed block). One interesting
thing about English-made concertinas is that their reeds, at least the steel
reeds, rarely wear out. Something to do with their design I would guess. I
did blow a reed in my Crabb concertina during a recent tour of Denmark and
Shetland, the first reed to go in that concertina since I bought it new in
1970. I've uploaded a couple of photos of the new reed I cut for it. One
photo shows it under construction and the other shows it fitted to its reed
shoe. Here's the link:
https://docs.google.com/document/pub?id=1nprVdLeSOPlq3J7qECgDDrR7xld9KNz60SOBW6m4BiMBest,
Rick
Great information Rick!
However, there are a few terms relating to accordians that I don't
understand. For example "cassotto", "cassotto tone chamber", "reed shoe",
"reed block" and "cabinet".
Is there a spot on the web that would clairfy these terms, and maybe teach
me a bit about accordians in general? Thanks in advance for any info.
Doug H
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.
