Bending

[Winslow Yerxa <76450.3230@xxxxxxxxxxxxxx>]

TO: internet:harp-l@xxxxxxxxxxxxxx

For those interested in Johno's paper, I suggest you contact him
at

JOHNO@xxxxxxxxxxxxxxxxxxxxxxxxxx

By the way, it is copyrighted, has arcane illustrations, and is
very tough reading for someone (like me) with little or no
background in physics.

I had a discussion with him about a year ago as to why an opening
reed (for instance, the blow reed that sounds when the draw reed
is bent all the way down in Hole 4) sounds a little less than a
semitone above its closing (normal) pitch. His reply:

      >The answer to your first question is simple - it's pure
      >coincidence. But first you need to realise that it's not
      >just that the opening reed plays a 1/2 a tone above the
      >"normal" sound (what i call the closing reed) but in fact
      >the closing reed is playing about 1/4 below the natural
      >reed pitch and the opening reed is playing about 1/4 tone
      >above it. By the natural pitch i mean the pitch when the
      >reed is plucked ie its natural vibration frequency. You can
      >easily verify this with a tuner. Actually the closing reed
      >is always a bit closer than the opening reed in pitch to the
      >natural reed pitch, but the point is that neither can sound
      >at exactly the reed pitch. The closing reed is always lower
      >in pitch and the opening reed is always higher in pitch.
      >This is shown in one of those diagrams where I have
      >measured the pitch using a strobe tuner.

      >Just how far apart the sounding pitch is from the natural
      >reed pitch is determined mainly by the properties of the
      >reed in particular the vibration damping of the material.
      >It is thus just coincidence that the total difference
      >between the pitch of the closing and opening reeds is 1/4 +
      >1/4 = 1/2 tone. This is one of the many accidental things
      >about the instrument. It has nothing whatsover to do with
      >numerology or ratios as in scale intervals, and in fact the
      >difference in pitch varies down to close to a 1/4 tone.

Bear in mind, we're talking here about a single reed IN
ISOLATION. Someone ventured that the other reed in the same hole
would have an effect on this pitch. You can easily verify that it
doesn't - the pitch of a note bent down all the way (like the
slightly flat C# emitting from the C blow reed during that draw
bend in Hole 4) doesn't change when you stop the draw reed with
your finger.

I have an all-blow Tombo single-reed bass harmonica where the top
two reeds can be overdrawn (no draw reeds in sight) to the usual
slightly-less-than-a-semitone, and then bent up several semitones
- so, yes, a bent note can be bent up. It depends on where you
start your measurement.


Danny Wilson states:

     Overblow and overdraw notes are usually used only as passing
     notes, and are extremely difficult to sustain. They also
     usually lack a "pretty" tone, and sometimes are more of a
     squeal or squeak by their very nature.

This is only true for a badly set up harp played wih poor
technique. A good quality overblow can be sustained indefinitely and will
yield a very full tone not unlike that of a French horn. Squeaks
and unpleasant overtones are not a necessary part of overblows or
overdraws.

Winslow Yerxa                    HIP - the
Harmonica Information Press             Harmonica
76450.3230@xxxxxxxxxxxxxx                       Information Publication