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David asked me to post this here and under Kinya's...

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Tue, 07/09/2019 - 17:26
nlm57
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...section of the forum to obtain an explanation as to why the following occurs, ie. what the reeds are doing;

 

"David, I'm starting to have some success at bending, but when, for instance, I hold the 4 draw bend for a while, sometimes I get a really high pitched metallic screeching like feedback. Am I playing too hard, or maybe bending a little beyond, (lower), than I need to. Or maybe both. Is this what's producing this phenomenon? It sort of hurts my left ear a little."

 

David wants me to report back as to what you say.

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Wed, 07/10/2019 - 04:58
#1
Expert Winslow Yerxa
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Inharmonics and persuasive bending

That metallic ringing you're hearing is an inharmonic overtone - one not based on multiples of the fundamental frequency of the reed. It'soften attributed to torsional vibration - the reed vibrating from side to side in addition to vibrating along its length. Some makes sof harmonica, notably Lee Oskars, are especially prone to torsional vibration, but it can happen with any harmonica.

What it means diagonstically is that your mouth is tuned to a note other than the bent pitch of Draw 4, and that you're achieving the bend more by force than by persuasion.

Try this:

  1. Start playing the unbent Draw 4 very softly.
  2. Without increasing the volume, slide the note down in pitch to a one-semitone bend and sustain it.
  • If the bend suddenly pops in, that still indicates that you're not really tuning your mouth to the note.
  • if you still hear the metallic ringing, again, you need to focus your oral cavity resonance.

So what do you need to do to make your bend more persuasive?

It's all in the tongue.

The tongue does two things to bend a note:

  1. It defines the back wall of the tuned chamber by narrowing the airflow with the K-spot - the humped up place on the tongue that also makes the K-sound, with the K-spot raised to the roof of your mouth.
  • When you inhale with the K-spot activated, you'll feel suction at that point, even when inhaling gently.
  • When you exhale through the K-spot, you'll feel air pressure at that point.
  1. It sizes the tuned chamber with two types of tongue action:
  • Sliding the K-spot forward or back along the roof of your mouth, like moving a slide along a guitar string. This moves the back "wall" of the tuned chamber to change the size of the chamber and tune it to lower (farther back for a bigger chamber) or higher (farther forward for a smaller chamber). When your tongue is on the harp, you have less front-to-back range of motion than you do when the tip of your tongue is free to move, but you still have some.
  • Raising and lowering the portion of your tongue that lies between the K-spot and the tip of your tongue. This is like raising and lowering the "floor" of the chamber to make it larger (lowering the floor) or smaller (raising the floor).

Play around with the K-spot and sizing the chamber at low volume (gentle breath flows) and you'll find how you can bend without squeals.

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Wed, 07/10/2019 - 12:11
#2
nlm57
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Thank you...

Thanks very much for the detailed explanation Winslow!

It was actually with a Lee Oskar harp that I experienced the ringing.

It didn't happen with a Special 20 or a Crossover.

I fired up Harp Ninja and found that I was bending the 4 draw down below the "floor" of the bend. Instead of the bent note being in the Green, it was very definitely in the Red. I may have been bending with too much force as well. And, as I might have mentioned, the ringing would show up after holding the bend for at least a few seconds, not in a typical playing situation. I was just practicing long tones, something I just recently started doing. It was then that the ringing showed up. I found your explanation fascinating.

Generally I play rather softly.

Thanks again

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Wed, 07/24/2019 - 23:04
#3
RB
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I had the very same thing on

I had the very same thing on my special 20.

Thought it was a reed catching the side of the slot. So I even tried widening the slot and centering the Reed..

I also lowered the gap. That affected the play significantly, as it forces me to play softer, and the bends are easier and more delicat now. With more sensitive bends on lowered gaping  I noticed that metallic sound happens when I bend too far. Similar toyour experience. So,playsofter is the solution for me

 

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