[Harp-L] Re: Harp-L Digest, Vol 37, Issue 18

["rick epping" <rickepping@xxxxxxxxx>]

Hi Rick,

I've pasted below an explanation I prepared when the XB-40 first came out.
The high blow bends on a C XB-40 can be bent without distorting but do, at
least for me, require a different technique to that normally employed on
regular diatonics.  Described in more detail below, the technique is
basically to make one's mouth cavity large by moving the tongue back instead
of small by moving the tongue forward.

Hopefully this will be of some assistance.

Best regards,
Rick


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High Notes on the XB-40



The range of notes easily obtainable on an XB-40 is determined at its upper
limit by the resonant frequency of the highest chambers relative to the
resonant frequency of the reeds occupying those chambers.  The smaller the
air space within a reed chamber, the higher its resonant frequency will be
and the higher pitched will be the reed that can be effectively used there.
The chambers in the highest holes of the XB-40 have been designed as small
as possible given the clearance requirements for the reeds and valves as
well as the requirements of the injection molding process by which the comb
is manufactured.



Some difficulty in playing can arise with the higher keys of XB-40, in
particular the highest keys of C and Db, where the resonant frequency of the
reeds in Hole 10 exceeds the resonant frequency of the chamber. In this
situation the chamber frequency can pull the oscillating frequency of a reed
downward in a phenomenon known as mode locking or frequency pulling.  The
greater the disparity between the higher frequency of a reed and the lower
frequency of its chamber, the more difficulty there can be in obtaining good
response.  It is for this reason that the key range for the XB-40, like that
of the chromatics, is set lower than that of the standard, single-reed
diatonics (C/C# is the highest chromatic key while high G is the highest
diatonic key).  The highest reed in a Hohner Richter 10-hole model such as
the Marine Band, the g4 reed from Hole 10 of a high G harp, would play flat
and with some difficulty if set over a Model 270 or 280 chromatic's highest
chamber, which is larger and has a lower resonant frequency than that of a
Hole 10 Richter chamber.  The difficulty would be greater still were that
same reed set over the highest chamber of an XB-40, which is actually a
double chamber - the inner valve chamber combined with either the upper blow
reed chamber or the lower draw reed chamber, depending on the direction of
airflow.  While the Hole 10 reeds in the lower XB-40 keys play easily, those
in the highest few keys may play with some difficulty as their resonant
frequency is higher than the resonant frequency of the Hole 10 double
chamber.



Adjustment of technique can help to minimize this problem.  For high notes
on harmonicas with small reed chambers, the player's tongue can be
positioned either forward in the mouth to create a resonant frequency in the
reed chamber/mouth cavity matching that of the reed being played or down and
back in the mouth to avail of the higher partials of the full vocal tract.  On
hole 10 in the higher keys of the XB-40 however, the player might not be
able to position the tongue forward enough to reach the resonant frequency
of the reed being played, resulting in an unintentional bend or a choked
note.  If the tongue is instead positioned back in the mouth to create a
fundamental resonant frequency one octave lower than that of the reed, the
second partial of this larger mouth cavity will then match that of the reed
and allow it to play.  From this position the tongue can be shifted upward
and forward for a bend.  Using this technique, the reeds in Hole 10 on an
XB-40 in the keys of C and Db are more playable, though they may still seem
relatively stiff compared to the reeds in the lower holes due to their
exceeding the resonant frequency of their reed chamber.



In conclusion, while the reeds in Hole 10 on the lower keys of the XB-40 are
quite playable they can be somewhat stiff in the highest keys, where their
resonant frequency is higher than that of the reed cell.  Use of a technique
such as described above can do much to improve the playability of these high
notes.

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On 9/8/06, harp-l-request@xxxxxxxxxx <harp-l-request@xxxxxxxxxx> wrote:
> Message: 11
> Date: Fri, 08 Sep 2006 10:46:33 +1000
> From: "Rick Dempster" <rick.dempster@xxxxxxxxxxx>
> Subject: [Harp-L] Re: XB Altered tunings--Melody Maker
> To: "rick epping" <rickepping@xxxxxxxxx>, <harp-l@xxxxxxxxxx>
> Message-ID: <45014A090200006600012843@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
> Content-Type: text/plain; charset=US-ASCII
>
> Rick,
>        I have just been looking at the chart for the XB, and I see
> that blow 2 should go down a whole tone. I have two of these beasts (C &
> A) and intend to purchase more. I don't remember if I checked both, or
> only one. However, I will take another look and see if there is anything
> amiss as you suggest.
>       At the risk of wearing out my welcome, can you bring me up to
> date on the problem with the upper octave, which seems to distort (ie
> harmonic squeeks) when blow bending.
>       I recall discussion on this when the XBs first made their
> appearance; something to do with the size of the channels, but I don't
> recall if there was a final remedy suggested.
>       This problem is a real disappointment because the rest of the
> instument is wonderful. If only the top octave was as good as the lower
> two!
>
> Many thanks,
> Rick Dempster